Fix type hints for modify_in_place overloads in Dataset

[arthurmccray]

This PR fixes type hints for Dataset, specifically to do with the overloading of Dataset.crop() and Dataset.bin() and modify_in_place:bool.

Previously, .crop() -> Dataset no matter what, leading to issues:

Now with the fix, everything works as expected.

There are 2 other main types of change in the file:

• changing np.isscalar(val) to isinstance(val, float|int) which is better handled by static type checkers
• ruff reformatted dataset.py in a few places due to line lengths--not sure why that hadn't happened previously

Also, I'm not quite sure why, but reveal_type from typing was actually working okay even with the old version... and this fix doesn't break it or anything so there's no problems there.

[arthurmccray]

@gvarnavi let me know if this makes sense to you as i know you've played with static type checkers quite a bit.

[gvarnavi]

lgtm, and makes my type-hinter happy!