Make getSupportedCodeFixes on LS so it can be proxied by plugins

[sheetalkamat]

Fixes #28966

This should also help with #51713 so that getSupportedCodeFixes can be proxied by plugins esp with our module conversion ts.getSupportedCodeFixes cannot be overriden.

[typescript-bot]

Thanks for the PR! It looks like you've changed the TSServer protocol in some way. Please ensure that any changes here don't break consumers of the current TSServer API. For some extra review, we'll ping @sheetalkamat, @amcasey, @mjbvz, @minestarks for you. Feel free to loop in other consumers/maintainers if necessary

[mjbvz]

Protocol changes look good to me

[jakebailey]

This seems reasonable to me, though I am not sure what to do about existing plugins which do this. Do any at all? Or was this solely just VS Code itself hacking the ts object?

[sheetalkamat]

Most plugins use this hack and would need to update their code but i am assuming many were using vscode proxy so it might not impact as many. But if we are anyways going to need plugins to update their code, then its better to get updated to new API than hack.

[jasonwilliams]

Most plugins use this hack and would need to update their code

Is there a right way we should be doing this? I'm happy to update our code if things have changed.