Continuing from #13696.

In the spirit of

There should be one-- and preferably only one --obvious way to do it.

I think we should deprecate (either via a warning, or via using the word "deprecated" in the docstring):

• np.Inf, np.infty, np.Infinity, np.PINF - these are worse ways to spell np.inf, and the doc already recommends the latter
• np.NINF - this is a worse way to spell -np.inf
• np.NAN, np.NaN - these are worse ways to spell np.nan, and the doc already recommends the latter
• np.NZERO, np.PZERO - these are weirdly capitalized compared to the other recommended constants, and are shorter as 0.0 and -0.0