Typing improvements for MultiIndex
SciPy 2023 sprint

@phofl @noatamir 

Typing improvements for MultiIndex #6

- [x] Add sortorder for MultiIndex.from_arrays
- [x] Add sortorder for MultiIndex.from_frame
- [x] Add names for MultiIndex.from_frame
- [x] Add name and names for MultiIndex.copy


Thanks @cnguyen-03 !