Use footnotes for numbered notes in tables

Documentation

In a few places, the docs include tables with numbered notes, similar to this:

Cheese	In Stock
Red Leicester	no
Camembert	yes (1) (2)

(1) it's a bit runny
(2) the cat's eaten it

Often the notes are written using simple numbered lists, which notably don't create links between the note references and their definitions. This can make viewing the notes somewhat tedious, particularly when the table is very long or when the same notes are shared by multiple tables.

Another way to format these notes is using Sphinx footnotes. Footnotes have the benefit of creating bi-directional links between the note entries and their references, which makes viewing a note and then navigating back to where you were much easier. The footnote definitions can be placed anywhere in the docs, so in particular they can be placed immediately after the table that references them. This is already done for a few tables in the current docs, e.g. in collections.abc.

I propose migrating some of the existing table notes to footnotes in cases where having the extra navigation links would be helpful. In particular, I think this would be useful for the format code tables in the datetime docs.

The result would look something like this:

Cheese	In Stock
Red Leicester	no
Camembert	yes [^1] [^2]

[^1]: it's a bit runny
[^2]: the cat's eaten it

Linked PRs

• gh-137743

Start with the format code tables in the datetime documentation and compare their numbered-note style with the footnotes already used in collections.abc. Convert the relevant notes to Sphinx footnotes where navigation helps, preserving the note content and table meaning; gh-137743 indicates that related work is already underway.