[CI] Enable License, Docs, Unacceptable language, and Format checks

[shahmishal]

The CI checks were disabled to help land the GitHub Actions config into the repository. However, we should try to resolve these checks as soon as possible.

license_header_check_enabled: false
docs_check_enabled: false
unacceptable_language_check_enabled: false
format_check_enabled: false

#1308

[grynspan]

unacceptable_language_check_enabled: false

Well now I'm curious.

[plemarquand]

@grynspan Here is the list: https://github.com/swiftlang/github-workflows/blob/a28eb2c8a16ac77b823088e75e51b5cd30f0c1c3/.github/workflows/soundness.yml#L41

[shahmishal]

** Checking for unacceptable language...
** ERROR:  ❌ Found unacceptable language:
Dockerfile:12:64:# https://github.com/swiftlang/swift-docker/blob/main/swift-ci/master/ubuntu/22.04/Dockerfile
Sources/Testing/ExitTests/ExitTest.swift:266:53:    // See https://github.com/wine-mirror/wine/blob/master/dlls/msvcrt/except.c
Sources/Testing/ExitTests/SpawnProcess.swift:227:11:      _ = kill(pid, SIGCONT)
Sources/Testing/Testing.docc/LimitingExecutionTime.md:21:15:If a test may hang indefinitely or may consume too many system resources to
Tests/TestingTests/IssueTests.swift:487:8:    // Sanity check that we parse types cleanly.
Tests/TestingTests/Support/CartesianProductTests.swift:40:8:    // Sanity-check the first element is correct. (This value is also

[stmontgomery]

I enabled one of these in #1312. I'll grab this and try to do the others

[grynspan]

I didn't name the kill() function

[plemarquand]

@grynspan you can ignore usages with a trailing comment like // ignore-unacceptable-language

see: https://github.com/swiftlang/sourcekit-lsp/blob/766f2c87a750bc3afbf1a5b08cc804e044b6c6ad/Sources/SwiftExtensions/Process%2Bterminate.swift#L35

[stmontgomery]

@grynspan you can ignore usages with a trailing comment like // ignore-unacceptable-language

And indeed that's what I'm doing