XWIKI-21966: Cannot exit horizontal drop-down menu using accessibility tools

[Sereza7]

Jira URL

https://jira.xwiki.org/browse/XWIKI-21966

Changes

Description

• Added an event listener to close the currently navigated dropdown with Escape

Clarifications

• When focusing menu dropdown, pressing escape will collapse it and focus the toggler.
• Handling the focus manually is a thing to avoid. In this case:
  • the focus is on an element that got hidden, so we should move it to somewhere where it makes sense to have it
  • we don't move it far from the context we were in (only a couple tabs away in most cases)
  • we move it to an known and expected node

Screenshots & Video

Video demo to highlight the new behaviour

Executed Tests

Manual tests, see the video demo.
This component is not automatically tested (see changes in #2078, which did not break any test), so no further testing.

Expected merging strategy

• Prefers squash: Yes
• Backport on branches:
  • 15.10.X : The changes are pretty safe and have a small scope.