[TASK] Deprecate various GeneralUtility methods

Some methods in GeneralUtility nowadays are wrappers to
native PHP methods. We encourage people to use the PHP API
directly.

* GeneralUtility::IPv6Hex2Bin()
* GeneralUtility::IPv6Bin2Hex()
* GeneralUtility::compressIPv6()
* GeneralUtility::milliseconds()

In addition, these methods are unused by Core
* GeneralUtility::linkThisUrl()
* GeneralUtility::flushDirectory()

Reasoning: In order to make our code less coupled, TYPO3 Core should
use native PHP where it makes sense, instead of relying on GeneralUtility
in all places.

Resolves: #91001
Releases: master
Change-Id: I9e3a2f4a4bb42facad2d79f959b36482dba23ec8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64091


Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Alexander Schnitzler <git@alexanderschnitzler.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Alexander Schnitzler <git@alexanderschnitzler.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>