[TASK] Make backdrop of wizards static

Multi-step wizards may contain a lot of different steps (e.g. in
localization or form management) and accidentally closing the wizard by
clicking the backdrop may lead to frustration.

To prevent this issue, the backdrop of such wizards is now static.

Resolves: #99102
Releases: main
Change-Id: I7e7adf6a8e30cc067fbadd73016cf01ec9bdf4d2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76639


Tested-by: core-ci <typo3@b13.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Frank Nägler <frank.naegler@typo3.com>
Reviewed-by: Frank Nägler <frank.naegler@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>