[TASK] Remove persistent cache in GeneralUtility::xml2array

The method GeneralUtility::xml2array uses a runtime cache and in addition
a persistent database cache. The database cache is triggered using the
"cache_hash" method in PageRepository, which is a frontend only component.
Since this approach is binding the common layer with the frontend layer,
this dependency is removed.

Resolves: #75609
Releases: master
Change-Id: I43bd92df6570502abbb5714b217f3ff0e32a588c
Reviewed-on: https://review.typo3.org/47663


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>