Use search element for admin's filter sidebar

[Tom Carrick]

Using a search landmark instead of a div will improve the accessibility for screen readers.

We should ensure that it has a different aria-label than any other search landmarks or elements with the search role on the page (e.g. search bar) see: ​https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/Search_role#labeling_landmarks

I didn't check if there are any of these other than the search bar.

[icastellanox]

I've made the pull request: ​https://github.com/django/django/pull/18256

[Natalia Bidart]

For further information, see description of the search element in ​this link, specifically:

The <search> element semantically identifies the purpose of the element's contents as having search or filtering capabilities.

[Sarah Boyce]

This appears to revert #34835 which was introduced in 5.1, makes me think we should backport this to 5.1 before the beta freeze and mark this as a release blocker if we are instead saying this is in fact more accurate. We would also need to update the release note added in #34835.
Otherwise, we can close this ticket as wontfix.

[Tom Carrick]

So... I feel uncomfortable with this phrasing a little. I think nav was an improvement, and this is a further improvement. It could be backported, I don't have a problem with that either, but I wouldn't go so far as to say that nav was wrong, just that this is "more right".