[!!!][TASK] Migrate pages_language_overlay into pages

The patch migrates all data from pages_language_overlay into pages,
and moves all API calls to overlay pages.

The following restrictions are set:
* Backend is always showing pages only for "sys_language_uid=0"
  for the page tree, element browser (e.g. "linking to default
  language page"), except where explicitly requested like the Page
  Module => Languages view.
* pid and sorting are always the same for all translations and
  their default language page
* Elements on a page are always keeping the field "pid" to the
  default language page (no change)
* Permission checks for Backend users are always made against
  the default language page (perms_* fields and webmounts)

Resolves: #82445
Releases: master
Change-Id: I62536e21d7110fa434c75fbd4470a3f53b79d260
Reviewed-on: https://review.typo3.org/51272


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Tested-by: Frans Saris <franssaris@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>