[BUGFIX] Load FlexForm Sections on new before save

FlexForm Section can be added before content element is saved.
This is done by ensuring that processedTca have a value for list_type.

Earlier the pi_flexform was ignored as the default values on create
before save was empty.

Resolves: #81684
Releases: master, 10.4
Change-Id: I62e03cbbd93e8785f58c24dad1e573e8b5e0202b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68152


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>