GDScript: Replace ptrcalls on MethodBind to validated calls

[vnen]

This improves the performance of typed calls to engine methods when the argument types are exact.

Using validated calls delegate more of the work the core instead of doing argument unpacking in the VM. It also does not need different instructions for each return type, simplifying the code.

[adamscott]

Approved during the GDScript team meeting. We only reviewed the PR on the form, not the content. We trust @vnen on the performance improvements.

[akien-mga]

Might be worth a rebase and re-testing to ensure it still works as intended, since it was authored more than 2 months ago and we merged a bunch of changes in the meantime.

[dsnopek]

This may have negative performance implications on calling functions in GDExtensions. GDExtensionMethodBind converts all validated_call()s to call() rather than doing a proper ptrcall(). This is definitely a bug/short-coming in GDExtension which we should fix (and it certainly can be fixed in a separate PR), but I just thought I'd point it out.

[dsnopek]

I've made PR #82794 to address the GDExtension performance issue I brought up in my previous comment. I've tested it with this PR, and it seems to be working fine (the automated godot-cpp tests pass).

[akien-mga]

Thanks!