[BUGFIX] Set timezone on TCA dbType input

The value from columns that are marked as "dbType" date(time) fields
in TCA configuration are now explicitly interpreted using UTC timezone,
when the string value has no timezone specifier given.
JS supplied values contain Z as specifier, while records from the database
(which are processed during copy operations) do not contain a timezone
specifier.
Local time was assumed by PHP in the latter case before, as we did not
pass an explicit timezone information to the DateTime constructor.

Therefore we now assure no timezone conversion will happen and no
time/date-offset will be added, by using UTC explicitly.

Resolves: #89914
Releases: master, 10.4, 9.5
Change-Id: I8e531ae5f3367c4493ce1e7db4bec0ef02311e24
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66670


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>