[TASK] Replace beginsWith method with strpos to reduce execution time

Use the native PHP method strpos instead of StringUtility::beginsWith
method. The beginsWith method runtime compared to a simple strpos check
is much higher.

Resolves: #78602
Releases: master
Change-Id: I608ed791ddd770a8de493e0796387a18b22ff2ce
Reviewed-on: https://review.typo3.org/50534


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>