[TASK] Add tests for Extbase DateTimeConverter

Some older PHP versions could not handle DateTime::createFromFormat()
with negative integers.

This change adds tests to show that this actually works.

Resolves: #73637
Releases: master, 10.4
Change-Id: Ief4112bee6d8fc95fa46dc84cb0cfc6b4a3faff1
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65834


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Alexander Schnitzler <git@alexanderschnitzler.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Alexander Schnitzler <git@alexanderschnitzler.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>