Core: some typing and cleaning in `BaseClasses.py`

[beauxq]

What is this fixing or adding?

(TypedDict, total=False) doesn't let us see which members are required. The new NotRequired lets us specify that.

---

__str__ automatically defaults to __repr__ so this is backwards:

    def __repr__(self):
        return self.__str__()

---

line 980, Using a variable in a type annotation doesn't work. We might be able to turn Region into a Generic, but I'm not sure that's worth it.

How was this tested?

just unit tests and type checkers