[TASK] Add more unit tests to GeneralUtility::trimExplode

Add unit tests to GeneralUtility::trimExplode in preparation of a
performance improvement patch. Test with whitespaces and alternative
delimiters.

Related: #66317
Resolves: #66323
Releases: master
Change-Id: I1fc12996fb3f990deb405f84f1c2758b1b1ce3a2
Reviewed-on: http://review.typo3.org/38526


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>