[TASK] Add aria-label to datepicker button

To make the functionality of the button that opens the datepicker clear
to screenreaders, an aria-label is added to the button.

Resolves: #102470
Releases: main, 12.4
Change-Id: I3c16c887cd148101fe225d65ea95a6f88dd1518b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83292


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>