By making it an `EscapeError` instead of a `LitError`. This makes it
like the other errors produced when checking string literals contents,
e.g. for invalid escape sequences or bare CR chars.

NOTE: this means these errors are issued earlier, before expansion,
which changes behaviour. It will be possible to move the check back to
the later point if desired. If that happens, it's likely that all the
string literal contents checks will be delayed together.

One nice thing about this: the old approach had some code in
`report_lit_error` to calculate the span of the nul char from a range.
This code used a hardwired `+2` to account for the `c"` at the start of
a C string literal, but this should have changed to a `+3` for raw C
string literals to account for the `cr"`, which meant that the caret in
`cr"` nul error messages was one short of where it should have been. The
new approach doesn't need any of this and avoids the off-by-one error.

Starting from cargo#13311, Cargo's compiler artifact message
uses Package ID specification as package's identifier format.

Detect `NulInCStr` error earlier.

By making it an `EscapeError` instead of a `LitError`. This makes it like the other errors produced when checking string literals contents, e.g. for invalid escape sequences or bare CR chars.

NOTE: this means these errors are issued earlier, before expansion, which changes behaviour. It will be possible to move the check back to the later point if desired. If that happens, it's likely that all the string literal contents checks will be delayed together.

One nice thing about this: the old approach had some code in `report_lit_error` to calculate the span of the nul char from a range. This code used a hardwired `+2` to account for the `c"` at the start of a C string literal, but this should have changed to a `+3` for raw C string literals to account for the `cr"`, which meant that the caret in `cr"` nul error messages was one short of where it should have been. The new approach doesn't need any of this and avoids the off-by-one error.

r? ```@fee1-dead```

fix(rust-analyzer): use new pkgid spec to compare

Starting from rust-lang/cargo#13311, Cargo's compiler artifact message
uses Package ID specification as package's identifier format.

Zulip topic: https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/proc-macro-test.20bootstrap.20and.20pkgid.20JSON

cc `@ehuss`

…m-ra

This reverts commit 6001c50.