Implement applyEdit in LSP for signal connecting

[Razoric480]

As per the discussion in #42416, when an external text editor is set, the Connect Dialog fails to actually enact any change into the script. The workaround currently is to disable external editor, connect your signals, then re-enable it (or work in an external editor even with it turned off.)

This PR implements the workspace/applyEdit server request, which can cause a connected client to insert or replace text - in this case, a blank method stub. By connecting to the EditorNode, we can detect the "script_add_function_request" signal and pass the new function along to the client.

## Known Issues

Currently, once the script has been saved, its changes are not detected by Godot, so the "Go to method" menu item fails, and it will try to add duplicate functions if it already exists. This is fixed by the as yet unmerged #48615, which forces a resync by the server whenever a script is saved.

That PR has been merged in, so it's no longer an issue - so long as you save your script.

[Arrow-x]

could this be cherry-picked to 3.x?

[Razoric480]

I have a 3.x version already coded up, but want to wait for this to get approved before I push that one.

[akien-mga]

Thanks!

[akien-mga]

This failed building after merge, seems like WorkspaceEdit is now defined twice: https://github.com/godotengine/godot/runs/3709439712?check_suite_focus=true

[Razoric480]

That's embarrassing. I've implemented a fix and made sure it compiled successfully on latest. What's the protocol, should I open a new emergency PR with it?

[akien-mga]

Yes, please do.

And no worry, the issue seems to stem from your previous implementation in #48615 which was merged in August, so was not available yet in this July PR. The lengthy PR review process is to blame :)

[Razoric480]

Done and done at #53070 , once it passes automated checks.

[PascalCzempiel]

I am on Version 3.4.4, and I still have this issue. I still need to do the "disable external editor" workaround. Did I misunderstand that this was supposed to be already fixed for 3.x as well? Or do I need to wait for version 4?

[Razoric480]

This is fixed in 3.x. I just tested it just now and it popped a new function.

I am unsure why it wouldn't work.

[PascalCzempiel]

I am using C# and Visual Studio Code, but from reading the issues I was under the impression, that this fix should work for that language as well. Am I mistaken in the first place, or should I document my exact situation with screenshots?

[Razoric480]

The language server is part of the gdscript module. It would need to be extended our refactored to support other languages.

[PascalCzempiel]

Ok, so, the bug is NOT fixed for C# yet, got it. Thanks for the quick answer though.