[BUGFIX] Use Sitematcher to fetch available languages

EXT:viewpage must use the SiteMatcher to get the available languages.

The join functionality has been removed as well to let users view a page
in a fallback language.

Resolves: #88001
Releaes: master, 9.5
Change-Id: Ibd0be7b2d169a7e8fb029905e3221fdd3ee5d69c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60338


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Tested-by: André Schließer <andy.schliesser@gmail.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: André Schließer <andy.schliesser@gmail.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>