DEPR: .select_dtypes accepts non-standard dtype references
xref #24541 

DataFrame.select_dtypes() accepts strings including:

- ``datetimetz``
- ``datetime64tz``
- ``period`` (this is currently not-implemented). 

These are non-standard names of dtypes, but not specific enough to the and should deprecated. An argument can be made that we should accept ``period`` to mean ``period[*]`` and ``datetime64[*, *]`` or something like this to select all sub-dtypes, but we con't really have any sytax to account for this.