[TASK] Introduce new functions to ArrayUtility and StringUtility

New helper methods are added to allow
to do the reverse of flattenPlain() in ArrayUtility,
that is ArrayUtility::unflatten().

In order to unflatten correctly, an explode function
which respects escaping characters was introduced to
StringUtility.

Releases: main
Resolves: #99054
Change-Id: If153f04c7371b6dbae173472077cdcb1b18152b8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76546


Tested-by: core-ci <typo3@b13.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Benni Mack <benni@typo3.org>