[TASK] Consistently use str_starts_with and str_ends_with

With PHP 8.0 and symfony/polyfill-php80 it is possible to use
native str_starts_with() and str_ends_with() methods.

This way, the methods

* StringUtility::beginsWith()
* StringUtility::endsWith()

are marked as deprecated.

Resolves: #95293
Releases: master
Change-Id: I46d15c2f8b93c5f8b487966b2015ebefb1711348
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71135


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Benni Mack <benni@typo3.org>