How to fix the recent `TypeAlias` addition

[damusss]

A recent PR marked types inside typing.py with TypeAlias, but that object is only available from python 3.10. We now know how it passed the checks: inside __init__.py we catch import errors, and importing TypeAlias from typing before 3.10 results in an import error, so pygame.typing becomes a missing module with no exception. Once a PR fixing this is merged, the unit test for typing can be merged and issues like this won't appear again.

We can fix this in two ways:

• remove the addition of TypeAlias
• version check the relevant bits of the files to use TypeAlias on 3.10+ but use the old system otherwise

The one choosing should be @zoldalma999 as they made the original PR. :3

[aatle]

Note that typing.py and typing.pyi should exclude TypeAlias in either case, because it is not guaranteed that typing_extensions will be available at runtime.

[ankith26]

The linked PR puts up what I think is the best fix for now.