[BUGFIX] Allow config.linkVars to be added for linking to pages with site config

Due to the refactoring yesterday, the TypoScript option
config.linkVars was removed, but is still a valid use-case to be added.

Resolves: #86054
Releases: master
Change-Id: I6d42c82f474668b62143982b8d9f2adf9b735935
Reviewed-on: https://review.typo3.org/58097


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Tested-by: Frans Saris <franssaris@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>