[FEATURE] Add backend layout PageTs provider

It is now possible to define backend layouts via PageTSConfig on every page.

Resolves: #61903
Releases: master
Change-Id: I121e6ac36eb961f1e1fb260034b89b44596fa00d
Reviewed-on: http://review.typo3.org/41632


Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benjamin Kott <info@bk2k.info>
Tested-by: Benjamin Kott <info@bk2k.info>