Code maintenance/69596 improve static hover cards by using templates

[EinLama]

Ticket

https://community.openproject.org/wp/69596

• [x] Wait for #21279 to be merged first.

Refactors hover cards to make use of HTML template elements. This conveys the correct semantic meaning, since an existing DOM element is copied and rendered in a different location -> exactly what a template should do.

This elegant change additionally allowed us to streamline the behavior of the HoverCardTriggerController for both async and sync hover cards.

Merge checklist

• [x] Added/updated tests
• [x] Added/updated documentation in Lookbook (patterns, previews, etc)
• [x] Tested major browsers (Chrome, Firefox, Edge, ...)