[TASK] EXT:form - cache merged YAML settings

Cache the merged YAML settings into the assets cache to improve the
performance.

Resolves: #82373
Releases: master, 8.7
Change-Id: I601364d5957f26f1b369b513534936820f72b78e
Reviewed-on: https://review.typo3.org/54106


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Henning Liebe <h.liebe@neusta.de>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Sebastian Fischer <typo3@evoweb.de>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>