[TASK] Make pagetree toggle switch accessible via keyboard

This change makes the toggle button accessible via keyboard
and sets the focus manually, so that the pagetree can be toggled
via pressing space or enter on the keyboard.

Resolves: #102426
Releases: main, 12.4
Change-Id: I6916cf1f19de288e961ecb0dab85c76241097d33
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83473


Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>