The language module changes configuration files and basic
instance system files and thus belongs to the install extension.

The patch moves the "Admin Tools" -> "Language" module to
"Maintenance" -> "Manage language packs" and comes with a
series of advantages:
* UX improvements and better overview
* Overall language pack update progress is much quicker
* Just a fraction of code needed
* No dependency to extension manager anymore
* Documentation extension has no hidden dependency to lang anymore

Change-Id: Ibcb9659dfacb5fda7c00ab2f39160f095e0cd154
Resolves: #84131
Releases: master
Reviewed-on: https://review.typo3.org/55998


Reviewed-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Tested-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Tobi Kretschmann <tobi@tobishome.de>
Tested-by: Tobi Kretschmann <tobi@tobishome.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>