[!!!][TASK] Remove deprecated AbstractPlugin

\TYPO3\CMS\Frontend\Plugin\AbstractPlugin

Resolves: #101003
Related: #100963
Related: #100639
Releases: main
Change-Id: I81ec99d4b9417e726b137c4eb15e217cdf0976d9
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79264


Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Thomas Hohn <tho@gyldendal.dk>