Remove typing_extenions at minpy 3.11

[Bryan Van de Ven]

We currently use Self, Never, and NotRequired from typing_extensions all of which are accepted starting with Python 3.11.

This is a placeholder issue to remember to update these cases to utilize stdlib typing instead, once it becomes possible.

Additionally, I would like to propose that after this, we strongly try to avoid taking on features from typing_dependencies in the future. Although we protect usage behind TYPE_CHECKING as policy, it's just one more thing to have to keep track of in some way.