[TASK] Migrate icon-element to @lit/task

@lit/task graduated from a 2-year @lit-labs phase, to an officially
supported helper library for lit elements. We want to start using it
as it embraces a tri-state model for async operations:

  * pending
  * complete
  * error

…which is important in order to always handle error cases instead of
silently ignoring them. Also existing or currently running requests are
aborted and/or ignored when a newer state has already been activated.

The icon-library deduplication caching strategy is refactored into a
reusable helper instance that is a bit more generic and allows to
abort (ref counted across duplicate requests) async operations.

Commands executed:

  npm install --save @lit/task
  npm run build

Resolves: #102308
Releases: main, 12.4
Change-Id: If068145a8bc87ae386af38aa6a63e4f19062345f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81683


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: Benjamin Franzke <ben@bnf.dev>