[BUGFIX] Reduce memory consumption in findIdentifiersByTag()

When searching cache-identifiers by tag, the Typo3DatabaseBackend now
utilizes DBMS functions for de-duplication of identifiers instead
of fetching all records and de-duplicate them afterwards in php space.
This dramatically reduces memory usage, when many duplicated identifiers
are in a cache table for any given tag.
Note that there is no noticable impact whenever there are no duplicates
at all, as the DBMS handles the de-duplication.

Releases: master, 9.5
Resolves: #89997
Change-Id: Ia28deee1e02eec9792dc4b0d4ce41e2177fcadf4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62749


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Jonas Eberle <flightvision@googlemail.com>
Tested-by: Susanne Moog <look@susi.dev>
Reviewed-by: Jonas Eberle <flightvision@googlemail.com>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Susanne Moog <look@susi.dev>