[TASK] Centralize Page Layout resolving

This change centralizes Frontend's "PageLayoutResolver",
used in TypoScript, and BackendLayoutView logic
to find the used page layout, while also modelling
more towards an object within PageLayout which can be
used at a later stage in FE to retrieve more information.

At the same time, some BackendLayoutView code is reduced
now.

Resolves: #103466
Releases: main
Change-Id: I716fe7313894aac92e5519a6b725feefff908270
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83567


Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>