Drop Python 3.8 support

[DavidRomanovizc]

What feature should we add?

Python 3.8 is EOL, So I think we need to drop Python 3.8 from version supported.

When we drop Python 3.8, we can use generic type-alias which are added in Python 3.9:

• PEP 585: e.g. typing.List[T] -> list[T], typing.Dict[KT, VT] -> dict[KT, VT], typing.Type[T] -> type[T]

If others agree, I can work on this :)

[pacrob]

Thanks for the offer, but we need to coordinate dropping/adding python versions across all our libs. Plus updates from our template. I'll leave this open, as it certainly needs to be done, but no need to work on it yourself.