CLEAN: Use `typing_extensions.override`

[Dr-Irv]

Throughout the stubs, we have ignores for overrides that we know are valid. We can use @override when we know that the override is correct.

Have to look for:

# type: ignore[override] # pyright: ignore[reportIncompatibleMethodOverride]

What I'm not sure of is that for places where mypy complains but pyright does not, if we include @override, whether pyright will complain saying something like it's an unnecessary override.

Should import override from typing_extensions, since it was introduced in python 3.12