[Doc][Python] Make docs release match arrow releases

[asfimport]

For docs that are shipped with new arrow releases (C++, Python) we should serve the documentation related to the arrow version.

At the moment for example if I want to look at the docs for 3.0.0 there is no easy way, the version I end up to is always the one for the current release. Or if I want to look at the doc for the current version under development there is no easy way.

We could for example deploy the docs under subdirectories that match the arrow version they refer to.

https://arrow.apache.org/docs/4.0.1/python/
https://arrow.apache.org/docs/5.0.0/python/
https://arrow.apache.org/docs/dev/python/

https://arrow.apache.org/docs/current could just become a redirect to the latest release

Reporter: Alessandro Molina / @amol-

Related issues:

• [Documentation] Documentation Improvements (is a child of)
• [Doc] Host different released versions of the documentation + version switcher (duplicates)

_{Note: This issue was originally created as ARROW-13411. Please see the migration documentation for further details.}

[asfimport]

Joris Van den Bossche / @jorisvandenbossche:
@amol- I am going to close this one as a duplicate of ARROW-13260