, bitcoin#21969, bitcoin#23653, bitcoin#23438, bitcoin#24190, bitcoin#24253, bitcoin#24231, bitcoin#26258, bitcoin#28012, partial bitcoin#25001, bitcoin#25296, bitcoin#23595, bitcoin#27927 (serialization updates)

2b26a87 merge bitcoin#28012: Allow FastRandomContext::randbytes for std::byte, Allow std::byte serialization (Kittywhiskers Van Gogh)
4eeafa2 partial bitcoin#27927: Allow std::byte and char Span serialization (Kittywhiskers Van Gogh)
cb2fa83 test: place the std::ostream operator<< definition in namespace std (Kittywhiskers Van Gogh)
cf4522f partial bitcoin#23595: Add ParseHex<std::byte>() helper (Kittywhiskers Van Gogh)
e4091aa partial bitcoin#25296: Add DataStream without ser-type and ser-version (Kittywhiskers Van Gogh)
eab031a merge bitcoin#26258: Remove unused CDataStream::rdbuf method (Kittywhiskers Van Gogh)
95b5850 partial bitcoin#25001: Modernize util/strencodings and util/string: string_view and optional (Kittywhiskers Van Gogh)
5fe72bb merge bitcoin#24231: Fix read-past-the-end and integer overflows (Kittywhiskers Van Gogh)
24af372 merge bitcoin#24253: Remove broken and unused CDataStream methods (Kittywhiskers Van Gogh)
baf8dd6 merge bitcoin#24190: Fix sanitizer suppresions in streams_tests (Kittywhiskers Van Gogh)
e933d78 merge bitcoin#23438: Use spans of std::byte in serialize (Kittywhiskers Van Gogh)
d3b2822 merge bitcoin#23653: Generalize/simplify VectorReader into SpanReader (Kittywhiskers Van Gogh)
2c32a09 merge bitcoin#21969: Switch serialize to uint8_t (Kittywhiskers Van Gogh)
0a08dbf merge bitcoin#21824: Replace deprecated char with uint8_t in serialization (Kittywhiskers Van Gogh)
d0b4e56 merge bitcoin#21966: Remove double serialization; use software encoder for fee estimation (Kittywhiskers Van Gogh)
1d6aafe merge bitcoin#21817: Replace &foo[0] with foo.data() (Kittywhiskers Van Gogh)
d9a8ce2 trivial: move GetSerializeSize away from Stream (Un)serialize functions (Kittywhiskers Van Gogh)

Pull request description:

  ## Additional Information

  * Dependency for #5902

  * [bitcoin#24231](bitcoin#24231) is merged after [bitcoin#24253](bitcoin#24253) due to a MinGW bug ([comment](bitcoin#24231 (comment)))

  * [bitcoin#25001](bitcoin#25001) is listed as unmerged despite being committed upstream as bitcoin@132d5f8

  * [bitcoin#25296](bitcoin#25296) is listed as unmerged despite being committed upstream as bitcoin@79e007d

  * [bitcoin#21966](bitcoin#21966) was partially backported in [dash#4197](#4197) as f946c68, including only 2be4cd9.
    The excluded commits have been backported, marking the pull request as fully merged.

  * [bitcoin#23438](bitcoin#23438) was partially backported in [dash#5574](#5574) as de54b87, including only fa65bbf.
     The excluded commits have been backported, marking the pull request as fully merged.

  * [bitcoin#27927](bitcoin#27927) opened a fresh can of hell thanks to being (possibly?) the first pull request to include `std::byte` `BOOST_CHECK`'s to the unit test suite. For reasons still unbeknownst to me, it refused to compile, despite being perfectly happy when checked-out as a commit directly and built as-is from upstream.

    The compile error was like this (edited for brevity):
    ```
      CXX      test/test_dash-serialize_tests.o
    In file included from test/serialize_tests.cpp:13:
    In file included from /src/dash/depends/x86_64-pc-linux-gnu/include/boost/test/unit_test.hpp:18:
    In file included from /src/dash/depends/x86_64-pc-linux-gnu/include/boost/test/test_tools.hpp:46:
    In file included from /src/dash/depends/x86_64-pc-linux-gnu/include/boost/test/tools/old/impl.hpp:24:
    /src/dash/depends/x86_64-pc-linux-gnu/include/boost/test/tools/detail/print_helper.hpp:53:13: error: static assertion failed due to requirement 'boost::has_left_shift<std::basic_ostream<char, std::char_traits<char>>, std::byte, boost::binary_op_detail::dont_care>::value': Type has to implement operator<< to be printable
                BOOST_STATIC_ASSERT_MSG( (boost::has_left_shift<std::ostream,T>::value),
                ^                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    [...]
    <scratch space>:206:1: note: expanded from here
    BOOST_PP_REPEAT_1
    ^
    test/serialize_tests.cpp:347:9: note: in instantiation of function template specialization 'boost::test_tools::tt_detail::check_frwd<boost::test_tools::tt_detail::equal_impl_frwd, std::byte, std::byte>' requested here
            BOOST_CHECK_EQUAL(out.at(0), std::byte{'a'});
            ^
    [...]
    In file included from test/serialize_tests.cpp:13:
    In file included from /src/dash/depends/x86_64-pc-linux-gnu/include/boost/test/unit_test.hpp:18:
    In file included from /src/dash/depends/x86_64-pc-linux-gnu/include/boost/test/test_tools.hpp:46:
    In file included from /src/dash/depends/x86_64-pc-linux-gnu/include/boost/test/tools/old/impl.hpp:24:
    /src/dash/depends/x86_64-pc-linux-gnu/include/boost/test/tools/detail/print_helper.hpp:55:18: error: invalid operands to binary expression ('std::ostream' (aka 'basic_ostream<char>') and 'const std::byte')
                ostr << t;
                ~~~~ ^  ~
    /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/cstddef:130:5: note: candidate function template not viable: no known conversion from 'std::ostream' (aka 'basic_ostream<char>') to 'byte' for 1st argument
        operator<<(byte __b, _IntegerType __shift) noexcept
        ^
    [...]
    5 warnings and 2 errors generated.
    make[2]: *** [Makefile:17842: test/test_dash-serialize_tests.o] Error 1
    make[2]: *** Waiting for unfinished jobs....
    make[2]: Leaving directory '/src/dash/src'
    make[1]: *** [Makefile:18525: all-recursive] Error 1
    make[1]: Leaving directory '/src/dash/src'
    make: *** [Makefile:802: all-recursive] Error 1
    ```
    * No such error was present on Bitcoin.

      It is true, that no `std::ostream& operator<<(std::ostream& a, const std::byte& b)` is present by default but attempting to `grep` for any specializations didn't show anything _relevant_ that Dash didn't have. Searching on GitHub didn't help either.
    * Then, assuming that perhaps Boost's assertion logic may have changed, upgraded the version of Boost to match the pull request at the time, Boost 1.81. That also did not do anything (and actually, caused a trailing slashes unit test to fail but doesn't cause any problem in Bitcoin because they got rid of their `boost::filesystem` usage by then).
    * If that isn't it, then let's try building Bitcoin with Dash's depends. It built successfully, ran successfully. The problem isn't in the dependency, it's in the codebase.
    * Since it seemed to be `std::byte` related, pull requests that are related to `std::byte` serialization were backported and `std::byte` serialization related changes needed for [dash#5902](#5902) were cherry-picked. That's why this pull request came to be. But it didn't help this particular issue (though it did smooth out the cherry-picks).
    * Running out of ideas, `gdb` is used to step through `serialize_tests`'s `class_methods` and understand why `BOOST_CHECK_EQUAL(out.at(0), std::byte{'a'});` is valid in Bitcoin but not Dash by finding the elusive `operator<<`. This is where things go from bad to worse.

      Turns out, when you build with `clang`, `gdb` loses the ability to do breakpoints by file. So, an attempt is made to use `lldb` (which btw, is called `lldb-16`, running `lldb` with yield an error if you're using the develop container) and it refuses to work, erroring `personality set failed: Operation not permitted`.

      Turns out, the [`docker-compose.yml`](https://github.com/dashpay/dash/blob/37f43e4e56de0d510110a7f790df34ea77748dc9/contrib/containers/develop/docker-compose.yml) needs the following additions:

      ```
        cap_add:
          - SYS_PTRACE
        security_opt:
          - "seccomp:unconfined"
      ```

      After making these changes, `lldb` works and then we resume trying to find `operator<<`. After too many hours and nimbly alternating between `next` and `step`, tried making a return to `gdb` (compiling with `gcc` this time with the appropriate `CXXFLAGS`) hoping for different results and a while later, realized that it cannot step through Boost's headers (it doesn't recognize the filenames) and then recompile it with `clang` and return to `lldb`.

      This was a wild goose chase.

    * After a lot of futile efforts to find the operator by stepping through `BOOST_CHECK_EQUAL`, a basic example addressing the static assertion (that a left shift operator must exist of `<type>` (here `std::byte`) for `std::ostream`) was added in

      ```c++
      std::ostream& ostr = std::cout;
      ostr << std::byte{'a'};
      ```

      ...and it compiled in both codebases.

      So the left shift that Boost is asserting doesn't exist does exist but it isn't being detected for some reason. Upon hovering the `<<`, VSCode highlighted the source of the definition as [`setup_common.h`](https://github.com/dashpay/dash/blob/96ac317c2714afcac1ff4e2df309f17149f42776/src/test/util/setup_common.h#L27-L32) thanks to the comment above it.

      Diffing between Bitcoin and Dash revealed the secret, the `operator<<` definition was placed under namespace `std` by [bitcoin#23497](bitcoin#23497) in bitcoin@f7086fd (see [change](https://github.com/bitcoin/bitcoin/blame/f7086fd8ff084ab0dd656d75b7485e59263bdfd8/src/test/util/setup_common.h#L29-L35)).

      That change has now been made in a separate commit.

  ## Breaking Changes

  Changes in serialization APIs will make backports predating [bitcoin#23438](bitcoin#23438) annoying but will _not_ change how data is stored on disk.

  ## Checklist:
    _Go over all the following points, and put an `x` in all the boxes that apply._
  - [x] I have performed a self-review of my own code
  - [x] I have commented my code, particularly in hard-to-understand areas **(note: N/A)**
  - [x] I have added or updated relevant unit/integration/functional/e2e tests **(note: N/A)**
  - [x] I have made corresponding changes to the documentation **(note: N/A)**
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

Top commit has no ACKs.

Tree-SHA512: 1d7c67f5fe282f78e24cb720828e5f1f48b6926006b903c28399938532cc5c470c175b00c8b80e9662c4467c1201e09ae6d1cd9b95e8b20ace5e4410c72c472e