[jextract] Propagate build plugin config to command

[madsodgaard]

Correctly propagates any configuration from swift-java.config to the command line tool, when using the build plugin.

Also fixes the docs to correctly specify the values of enum options, as they use camelCase and not kebab-case.

[ktoso]

Thanks for the fix but we should approach this differently,

make all CLI options optional and only "override" the config values if they were set. This way we don't have to go to the plugin and pass strings anywhere, and it more models what we actually want:

func configure<T>(_ setting: inout T, overrideWith value: T?) {
  if let value {
    setting = value
  }
}

and

    config.outputJavaDirectory = outputJava
    config.outputSwiftDirectory = outputSwift
    configure(&config.unsignedNumbersMode, overrideWith: unsignedNumbers) <<<<
    config.minimumInputAccessLevelMode = minimumInputAccessLevel
    config.memoryManagementMode = memoryManagementMode

The problem is @Flag which does not support Bool? huh... so we need to figure that one out 🤔 Perhaps by manually parsing the command line arguments to see if it was passed or not?

[ktoso]

LGTM thanks for adjusting how we do this :)

[ktoso]

We're having CI issues... I'll see what I can do about that, sadly 6.2 didn't get the fix yet we're waiting on