Go 1.4 introduced TLS 1.3 by default, which we can't do since a lot of our clients depend on 1.2.
In order to disable 1.3 Go added new `MaxVersion` option to `tls.Config` structure.
For example one of 1.3 breaking "features" is the inability to explicitly set TLS ciphers (in 1.3 they should be picked automatically), and a lot of enterprises depend on it.

In order to make it non-breaking change I added new max SSL version attributes to all needed sections (everywhere where there is min version), and it is set to 1.2 by default.

New config fields:
`http_server_options.max_version`
`proxy_ssl_max_version`
Api definition fields:
`proxy.transport.ssl_max_version`

Additionally, fixed a bunch of tests (not related to 1.5 change from what I see).

All the vendoring removed as well!

As part of QA we need to ensure that all outbound and inbound Gateway calls use TLS 1.2, which includes:
- [ ] Uptime tests
- [ ] JSVM HTTP calls
- [ ] Batch API
- [ ] Reverse proxy
- [ ] Gateway -> Dashboard communication
- [ ] Gateway -> MDCB communication
- [ ] UDG GraphQL and JSON data sources

<!-- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)
- [ ] Refactoring or add test (improvements in base code or adds test coverage to functionality)

<!-- Go over all the following points, and put an `x` in all the boxes that apply -->
<!-- If you're unsure about any of these, don't hesitate to ask; we're here to help! -->
- [x] Make sure you are requesting to **pull a topic/feature/bugfix branch** (right side). If pulling from your own
      fork, don't request your `master`!
- [x] Make sure you are making a pull request against the **`master` branch** (left side). Also, you should start
      *your branch* off *our latest `master`*.
- [x] My change requires a change to the documentation.
  - [ ] If you've changed APIs, describe what needs to be updated in the documentation.
  - [ ] If new config option added, ensure that it can be set via ENV variable
- [ ] I have updated the documentation accordingly.
- [x] Modules and vendor dependencies have been updated; run `go mod tidy && go mod vendor`
- [ ] When updating library version must provide reason/explanation for this update.
- [x] I have added tests to cover my changes.
- [x] All new and existing tests passed.
- [x] Check your code additions will not fail linting checks:
  - [x] `go fmt -s`
  - [x] `go vet`

Go 1.4 introduced TLS 1.3 by default, which we can't do since a lot of our clients depend on 1.2.
In order to disable 1.3 Go added new `MaxVersion` option to `tls.Config` structure.
For example one of 1.3 breaking "features" is the inability to explicitly set TLS ciphers (in 1.3 they should be picked automatically), and a lot of enterprises depend on it.

In order to make it non-breaking change I added new max SSL version attributes to all needed sections (everywhere where there is min version), and it is set to 1.2 by default.

New config fields:
`http_server_options.max_version`
`proxy_ssl_max_version`
Api definition fields:
`proxy.transport.ssl_max_version`

Additionally, fixed a bunch of tests (not related to 1.5 change from what I see).

All the vendoring removed as well!

As part of QA we need to ensure that all outbound and inbound Gateway calls use TLS 1.2, which includes:
- [ ] Uptime tests
- [ ] JSVM HTTP calls
- [ ] Batch API
- [ ] Reverse proxy
- [ ] Gateway -> Dashboard communication
- [ ] Gateway -> MDCB communication
- [ ] UDG GraphQL and JSON data sources

<!-- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)
- [ ] Refactoring or add test (improvements in base code or adds test coverage to functionality)

<!-- Go over all the following points, and put an `x` in all the boxes that apply -->
<!-- If you're unsure about any of these, don't hesitate to ask; we're here to help! -->
- [x] Make sure you are requesting to **pull a topic/feature/bugfix branch** (right side). If pulling from your own
      fork, don't request your `master`!
- [x] Make sure you are making a pull request against the **`master` branch** (left side). Also, you should start
      *your branch* off *our latest `master`*.
- [x] My change requires a change to the documentation.
  - [ ] If you've changed APIs, describe what needs to be updated in the documentation.
  - [ ] If new config option added, ensure that it can be set via ENV variable
- [ ] I have updated the documentation accordingly.
- [x] Modules and vendor dependencies have been updated; run `go mod tidy && go mod vendor`
- [ ] When updating library version must provide reason/explanation for this update.
- [x] I have added tests to cover my changes.
- [x] All new and existing tests passed.
- [x] Check your code additions will not fail linting checks:
  - [x] `go fmt -s`
  - [x] `go vet`