[BUGFIX] Toggle preview state in Form Editor

When the form is in "Preview" mode and an integrator either saves or
switches to the form settings, the stage itself is updated to be in
"Edit" mode again, but the internal state remains in "Preview" mode,
causing glitches in the UI.

This patch now disables the preview state in the form model everytime
the "stage area", containing the editing interface, is rendered.

Resolves: #102031
Releases: main, 12.4, 11.5
Change-Id: I84b0817bb99201527dbd4b950e560631e7b1d94f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81253
Reviewed-by: Benjamin Franzke <[email protected]>
Tested-by: Benjamin Franzke <[email protected]>
Reviewed-by: Andreas Fernandez <[email protected]>
Tested-by: Stefan Bürk <[email protected]>
Reviewed-by: Stefan Bürk <[email protected]>
Tested-by: Andreas Fernandez <[email protected]>
Tested-by: core-ci <[email protected]>