Update to Sphinx 7

[AA-Turner]

This enables using new features in Sphinx 5, including better index entry searching, object descriptions in the table of contents, and support for newer versions of Docutils.

I suggest bumping the version for all active versions

A

• PR: GH-99380: Update to Sphinx 7 #99381

• PR: [3.12] GH-99380: Update to Sphinx 7 (GH-99381) #114341

• PR: [3.11] GH-99380: Update to Sphinx 7 (GH-99381) #114342