[TASK] EXT:form - improve width of form editor stage

Improve and expand the width of the form editor stage for different
modes.

Resolves: #82324
Releases: master, 8.7
Change-Id: Ib98e21ed498a76a32b285d29dc186f09c097742a
Reviewed-on: https://review.typo3.org/54022


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Daniel Lorenz <daniel.lorenz@extco.de>
Tested-by: Daniel Lorenz <daniel.lorenz@extco.de>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>