[TASK] Streamline BackendUtility::getPagesTSconfig

BackendUtility::getPagesTSconfig does accumulate the PageTS
of a page, parses and returns it. That is the main purpose of
that method. But there are 2 method arguments that change the
behavior of that method. When setting $returnPartArray to true,
the PageTS will be returned non parsed. When providing a custom
$rootLine, that rootline will be used and the result is not
cached.

1.) There is just one method call in the core that makes use
    of the argument $returnPartArray, thus, fetching the non
    parsed PageTS is made available through a separate method
    called getRawPagesTSconfig(). Using the argument
    $returnPartArray is deprecated and will be removed.

2.) Providing a custom rootline via the $rootline method is
    also deprecated and will be removed. The core does not have
    the need to fetch the PageTS for a made up rootline, thus
    people can use getRawPagesTSconfig() with a custom
    rootline in the future and then parse that PageTS
    themselves. That way the result of getPagesTSconfig can
    always be cached in the future.

Resolves: #82497
Releases: master
Change-Id: I764324072d962e89e37bf514fa405e3cd93d2783
Reviewed-on: https://review.typo3.org/54152


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>