Improve localTimeAgo rendering

What does this MR do?

• Moves Tooltip creation for timeago elements to requestIdleCallback
• Memoizes localization of timeago
• Removes unneeded class js-timeago-render

Results:

On a page with 12 js-timeago instances we can see the following measurements:

Commit	Time spent in localTimeAgo	Time spent on localTimeAgo > gettext	s__ function calls	Profile
227ce776 (Baseline)	20ms	11ms	336 calls	00-profile-227ce776dcd.json.tar.gz
636c36bb (Moving modal creation to requestIdleCallback)	15ms	11ms	336 calls	01-profile-636c36bbbfa.json.tar.gz
6e4dac35 (Memoizing localization)	3.49ms	0.4ms	6 calls	02-profile-6e4dac3589d.json.tar.gz

We notice that we had 28 s__ calls per js-timeago instance. This is consistent with the current pattern of retrieving all translations for each js-timeago by recreating the array over and over. Once we memoize the function, we have a maximum of 28 calls per page. In normal use cases we probably just see 8-10 calls per page.

What are the relevant issue numbers?

• Closes #56327 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer

Closes #56327 (closed)