[BUGFIX] Allow XCLASSing of WorkspaceRecord

The factory method WorkspaceRecord::get() now uses a proper
makeInstance() call instead of new for creating new instances,
which allows XCLASSing the class and aligns object creation
to "the TYPO3 way" in that place.

Also add a regression test.

Resolves: #97423
Relates: #97754
Releases: main, 11.5
Change-Id: I76e5ce3a1f908bf0efa4faaa439724e2d1d7cbb2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74960


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>