[TASK] Testing Framework: Move fluid base test and ensure BC

After the merge of #79025 now the fluid base test case for viewhelpers
should be moved to the testing framework.

A compat layer for the old namespaces is introduced.

Additionally some small leftovers in documentation and CI configuration were fixed.

Change-Id: I78b9670a1ee1fadb4f4c36265c3a51cd1e879e50
Releases: master
Resolves: #79075
Reviewed-on: https://review.typo3.org/51023


Tested-by: Helmut Hummel <typo3@helhum.io>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Helmut Hummel <typo3@helhum.io>