[BUGFIX] Correct file language overlay for pages

This patch corrects the fields the FILES content object is using for
doing the language overlay for file references for fields in the pages
table.

Instead of the _LOCALIZED_UID that is only available for other record
types the _PAGES_OVERLAY_UID field is now used to check if there
is a translated version available.

Resolves: #47869
Releases: 6.2, 6.1, 6.0
Change-Id: I2465a9e3ccd49223cc44885ffba8484788e1b669