[BUGFIX] Re-enable menu configuration caching

It is ensured that the menu configuration is always an array.

The PageRepository::getHash() method is extended to return the
raw cache content. This allows to cache empty arrays.

Change-Id: If92c80feabb8e68b66497827667b9fd0ab1c214e
Resolves: #63550
Releases: master, 6.2
Reviewed-on: http://review.typo3.org/35002


Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Reviewed-by: Arjen Hoekema <arjenhoekema@gmail.com>
Tested-by: Arjen Hoekema <arjenhoekema@gmail.com>
Tested-by: Markus Klein <klein.t3@reelworx.at>