[TASK] Properly disable task setting fields

In its current implementation, the scheduler module renders all
settings fields (aka "additional fields") at one and toggles their
visibility depending of the selected scheduler task that is about to
get created.

When submitting the form, the field are now properly disabled to
prevent their submission, instead of moving the fields out of the form
in a `submit` event handler.

Resolves: #101806
Releases: main
Change-Id: I8428aa6d60b365348310d35de6303e4f9d4c77a0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80769


Tested-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: core-ci <typo3@b13.com>