[TASK] Avoid vfsStream in functional tests

There is little reason to fake filesystems
details within functional tests that use an
isolated instance.

Resolves: #98923
Related: #97762
Releases: main
Change-Id: I83579eab82655c4cd464050e4fbcd7608ba0062e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76268


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>