MAINT: Remove `np.int_` and `np.uint`
Hi!
This PR addresses changes that will be shipped in https://github.com/numpy/numpy/pull/24794 - deprecation of `np.int_` and `np.uint`. An explanation of changes:

- In places where `np.int_(value)` was used I replaced it with backward compatible `np_long(value)`.
- If dtypes were directly compared I replaced `np.int_` with `np.dtype(int)` (they are equivalent).
- For `dtype=` arguments I used `int` for conciseness.

Thanks again @mtsokol  I think I need to add one warning filter, similar to scipy https://github.com/scipy/scipy/pull/19341 that I did today - in case you experience failures with the current numpy nightly.  These changes should be reverted in https://github.com/pandas-dev/pandas/pull/55505, and also reverse-backported to 2.1.x. 