PERF: masked ops for reductions (min/max)

[jorisvandenbossche]

Follow-up on #30982, adding similar mask reduction but now for min/max.

[simonjayhawkins]

since mypy is a static checker, min and max will resolve to Any.

something to consider is that maybe could do something like

def min(values: np.ndarray, mask: np.ndarray, skipna: bool = True):
    return _reduction(np.min, values=values, mask=mask, skipna=skipna)


def max(values: np.ndarray, mask: np.ndarray, skipna: bool = True):
    return _reduction(np.max, values=values, mask=mask, skipna=skipna)

and remove _minmax and move func into reduction signature.

This issue occurs elsewhere in the codebase, so this is not a blocker, but may give more confidence in the refactors.

alternatively, would using functools.partial be clearer. (newer versions on mypy might support this better)

[jorisvandenbossche]

OK, adapted as you suggested (it gives an extra function call in runtime (instead of only at import time), but that should be negligible)

[jreback]

lgtm. some comments by others.

[jreback]

thanks @jorisvandenbossche