Pedro J. Estébanez

@mrTag, thanks to your test case, I've spotted a couple of issues. They are fixed now.

Rebased for 4.1, by the way.

Pushed after a rebase that simplifies the management of thread ids.

Pushed with an additional change, expanding the scope of the benefits of this PR (see update 3 in the description).

> * I think it needs to wait until [Refactor Node Processing to allow Scene Multithreading #75901](https://github.com/godotengine/godot/pull/75901) is merged, as it rewrites CallQueue in a way that is incompatible with...

If your PR is going to be merged soon, I can rebase this once more when that happens, but from that point on I won't be able to spend more...

I've rebased on top of #75901 and based it on the `WorkerThreadPool`, as requested. See _Update 6_ in the PR description for further info.

> This PR may also fix #75841 @akien-mga, I'm adding bugs I'm finding that may be fixed by this to the description of the PR, so they get this: ...

@m4gr3d, can you please test with #77229?

@venilark, do you think you could apply https://github.com/godotengine/godot/pull/88561 locally and try to reproduce the issue to see if that PR fixes it?