[BUGFIX] Native date and datetime values do not consider timezone

The TCA configuration property "dbType" allows to store "date"
or "datetime" values directly in the database (instead of using
a timestamp value).
However, the timezone is not recognized correctly - besides that,
the serverTimeZone is applied which does not make much sense at
all, since it leaves out DST handling.

Fixes: #51918
Releases: 6.0, 6.1, 6.2
Change-Id: I45da65d8cee2611358303e93305cb5c793223746
Reviewed-on: https://review.typo3.org/25367
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader