[TASK] Improved form editor hints and validations

- improved margin between field and hint for "special form" element
- styled custom error message hint -> this also applies for
  "single select" element : "inactive option"
- fixed validator and finisher margins
- styled hints for required textareas

Resolves: #82339
Releases: master
Change-Id: I3cd215eb967ccd6f0901a72675513a2619521d11
Reviewed-on: https://review.typo3.org/56981


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>