[TASK] fix override label in formengine

This patch ensures that we do not display override "" but a more useful
information. Additionally the checkboxes are enabled by default if no
default value available to reduce the effort needed to provide an
element specific value.

Resolves: #75540
Releases: master
Change-Id: I11667232761968c077f02ec18e6802d7e54fcc6f
Reviewed-on: https://review.typo3.org/47618


Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>