[TASK] Integrate "Functions" as context menu

The patch integrates ext:wizard_sortpages and ext:wizard_crpages
as context menu items in "more" of the page record context menus
and gets rid of the two default "Functions" main module entries,
effectively obsoleting ext:func, which will be extracted to TER
for b/w compat in a second step.

* Isolate ext:func by moving its language xml from ext:lang to ext:func
* Routing configuration for "sort pages" and "create pages" in ext:backend
* Context menu handling for "sort pages" and "create pages" in ext:backend
* Free "sort pages" and "create pages" from dependency to ext:frontend
  by not calling PageRepository->getMenu() anymore
* Proper use of request/response instead of _GP access
* Better controller / view separation

Change-Id: I2c7acbb79ddd8404fbef69a1c126d250b976629b
Resolves: #81768
Releases: master
Reviewed-on: https://review.typo3.org/53377


Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>