Fix resource loader not resolving shallow loaded scripts through dependencies

[beev1s]

When a script first gets shallow loaded through a dependency and and then requested by the resource loader, that script is already registered in ResourceCache and will therefore not be properly reloaded, which is necessary in order to resolve any Script inheritance. This can lead to errors when assigning objects with that script to a reference of its parent.

GDScript now overwrites set_path_cache which does not register it in the RessourceCache. set_path_cache replaces a call to set_path in get_shallow_script. get_full_script now calls set_path to register the script.

• Fixes Validation error using Resource sub-classes and sub-resources with specific combination of preload/@onready/instantiation #95909

[dalexeev]

Looks reasonable to me. I tested it, this PR fixes the linked issue.

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[Repiteo]

Thanks, and congratulations on your first contribution! 🎉