Improve core and GDScript VM multithreading performance

[DAShoe1]

Tested versions

4.x

System information

Windows 11

Issue description

Maybe this is a better place to implement this, although I don't believe it breaks compatibility. I created a PR for this for Redot 4.3, Redot-Engine/redot-engine#971 where I backported a Godot PR to Redot 4.3. I can create a PR in this repo for it as well if there is interest. It is a big performance boost for my project.

Steps to reproduce

Any script running in multiple threads.

Minimal reproduction project (MRP)

N/A