[BUGFIX] Unhide page translations by default

In TYPO3 v8, new page translations within pages_language_overlay
were visible by default when using plain DataHandler.

In TYPO3 v9, due to the merge into "pages" for translations,
the default value for "hidden" is used. Every new page translation
is now hidden by default - this is a different behavior.

Tests had to be modified to make this work again. However,
the change now removes the "hacks" within the tests,
and adds the functionality to take-over the "hidden" flag
from the default record.

For future TYPO3 major versions, the hidden field could be migrated
into a "allowLanguageSynchronization" once the Context API
is used throughout Core properly.

Resolves: #88248
Releases: master, 9.5
Change-Id: I2a684a0d4225451c3fbfc0021c09935c1224aaca
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60632


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Richard Haeser <richard@maxserv.com>