[TASK] Add label to toolbar search field

Add a label to the search field via aria-label attribute, because a
separate all time visible label would break the design.

Also disable pointer-events for the icon so the search field
is focused when you click on the icon.

Resolves: #92644
Releases: master
Change-Id: If897e458efc0c0caf1958391b8f7ddbeca92f9f7
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66276


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Michael Telgkamp <michael.telgkamp@mindscreen.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Michael Telgkamp <michael.telgkamp@mindscreen.de>
Reviewed-by: Benni Mack <benni@typo3.org>