[Docs] Add version dropdown to the sphinx docs

[asfimport]

As part of ARROW-13260, we need to add a version dropdown to the sphinx theme layout.

There is working happening for this in the upstream theme (pydata/pydata-sphinx-theme#436), but since that is not yet merged/released, I will "backport" it to our own docs.

Reporter: Joris Van den Bossche / @jorisvandenbossche
Assignee: Joris Van den Bossche / @jorisvandenbossche

PRs and other links:

• GitHub Pull Request #11283
• GitHub Pull Request #11563

_{Note: This issue was originally created as ARROW-14189. Please see the migration documentation for further details.}

[asfimport]

Krisztian Szucs / @kszucs:
Issue resolved by pull request 11283
#11283