Add a subcommand to sourcekit-lsp that automatically reduces sourcekitd issues

[ahoppen]

Essentially, this is adding three pieces of functionality:

1. sourcekit-lsp run-sourcekitd-request takes a JSON sourcekitd request and a path to sourcekitd.framework and executes that request using that sourcekitd. This is basically equivalent to sourcekitd-test -json-request-path but it works even if the toolchain with sourcekitd.framework doesn’t have a sourcekitd-test.
2. sourcekit-lsp diagnose --request-file takes a path to a JSON sourcekitd request, gets the source file’s contents from disk and reduces the source file + compiler arguments to create a reduced reproducer. It then copies all files referenced from the compiler arguments to a temporary folder and asks the user to file an issue with that information. To reproduce non-crashes an NSPredicate can be passed via the --predicate parameter. Any sourcekitd response that satisfies the predicate is considered a reproducer.
3. sourcekit-lsp diagnose without arguments is similar to (2) but looks in OSLog for the last sourcekitd crash.

---

So far, this tool has been able to automatically reduce a crash I found while working on sourcekit-lsp to the following input file and reduced the compiler arguments to only include the input file itself.

public actor TranslatableName {

  init(
    definitionName: String,
    definitionDocumentUri: DocumentURI,
    definitionPosition: Position,
    definitionLanguageService: any ToolchainLanguageServer,
    isObjectiveCSelector: Bool
  ) {
    self.isObjectiveCSelector = isObjectiveCSelector
  }
}

[ahoppen]

@swift-ci Please test Windows

[ahoppen]

@swift-ci Please test Windows

[ahoppen]

@swift-ci Please test macOS

[ahoppen]

@swift-ci Please test Linux

[ahoppen]

Merging this as-is so I can iterate on it in-tree. I will address review comments in follow-up PRs.

[bnbarham]

Very cool!

[bnbarham]

Our requests are really yaml aren't they? Why do we keep calling it JSON everywhere?