[DOCS] Document usage of YAML loader

The Form Framework ships its own YAML loader and
does not consistently use the YAML loader of the
TYPO3 core. The patch documents the reasons and
shows when which loader is used. Additionally,
some inconsistencies are fixed with this patch.

Resolves: #93579
Releases: master, 10.4
Change-Id: Ia1e091a4d54e714ca31ce44aed6c61cf994fe2d9
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70496


Tested-by: Lina Wolf <112@linawolf.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Lina Wolf <112@linawolf.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>