[BUGFIX] Fix language synchronization for inline relations with inline relations

If the language synchronization process is called on an inline
relation within another inline relation when there is more
than one language which should be synchronized, the process
fails with the following exception:

    #1486233164: Child record was not processed

The problem happens because of a non-unique cache identifier
which leads to incomplete operation.

Resolves: #81314
Resolves: #85168
Resolves: #85914
Releases: master, 9.5, 8.7
Change-Id: Icbfc96e5dae387b620e917db168e9e14de5f3820
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60722


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>