ENH: Reflect changes from `numpy` namespace refactor Part 3
Hi!
Due to NumPy's main namespace being changed in https://github.com/numpy/numpy/pull/24376, here I update NumPy's imports/aliases: e.g. `np.NaN` and `np.infty` won't be available anymore. Also, a canonical name for NumPy's `float` and `complex` should be used, which are `np.float64` and `np.complex128`.

`sctypes` will be removed from the top namespace, but its destination is not decided yet - therefore I import it from internal `np.core` for now. 
Thanks @mtsokol 