[TASK] Add be_user id to LinkGenerator page-version test context

Some of the previous todos were failing because the test context
contained a workspace id, but missed a backend user id.
In that case the workspace id was ignored by the test
framework (see TYPO3\JsonResponse\Middleware\BackendUserMiddleware).

This patch also adapts the SlugLinkGeneratorTest to check link
generation to versioned record both with and without a backend user
authentication.

Releases: master, 9.5
Resolves: #87973
Change-Id: I0a2ec41234963fd8af0ed3adf951f139f1e85215
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60302


Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>