xref https://docs.scipy.org/doc/numpy/reference/routines.sort.html

Extracted from #70:

• np.argmax
• np.argmin
• np.argwhere
• np.compress
• np.nonzero
• np.flatnonzero
• np.where
• np.searchsorted
• np.extract

(see #2077 for nanargmax/nanargmin)

Notes:

• argwhere/flatnonzero/extractcould should just be minimal wrappers around nonzero
• searchsorted is harder: it need would need low-level routines/wrappers for efficient binary search, which to my knowledge do not currently existing in XLA