DEPR: .consolidate() should be non-public
no user reason to use this, and will eventually disappear in pandas 2.0 anyhow.

I would rename to ``_consolidate()`` and then provide a deprecation warning for ``.consolidate()``. Would need to change some internal code to use the renamed version.

xref https://github.com/pandas-dev/pandas/issues/15482#issuecomment-281986233

