[!!!][TASK] Unify _PAGES_OVERLAY_UID and _LOCALIZED_UID

When doing language overlays in PageRepository
an overlaid language for a page received special properties:

* "_PAGES_OVERLAY_UID" (the UID of the translated page)
* "_PAGES_OVERLAY" (a flag indicating that a translation happened)
* "_PAGES_OVERLAY_LANGUAGE" (the sys_language_uid record)
* "_PAGES_OVERLAY_REQUESTEDLANGUAGE" (info which language was requested)

For regular records (non-pages) only one special property
was used "_LOCALIZED_UID".

This patch unifies the properties, as this was a historical
technical debt due to "pages" vs. "pages_language_overlays"
and other records.

"_PAGES_OVERLAY_UID" is replaced with "_LOCALIZED_UID",
"_PAGES_OVERLAY" is removed as a isset check for "_LOCALIZED_UID"
can be used
"_PAGES_OVERLAY_LANGUAGE" is replaced in favor of the native "sys_language_uid"
field
"_PAGES_OVERLAY_REQUESTEDLANGUAGE" is replaced with "_REQUESTED_OVERLAY_LANGUAGE"
and now also available for non-page records

As seen in the changes, some code can now be simplified
due to superfluous checks on "_PAGES_OVERLAY_UID" and directly
using "_LOCALIZED_UID".

Releases: main
Resolves: #102627
Change-Id: I7b5c9de66cccc4d2f0907d4d9c51a5b66aa4d4e8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82300


Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>