Using the projectstorage mechanism we introduce a flag for the test, so
we can use ProjectStorageInterface instead of ProjectStorage. It has the
overhead of a virtual function interface but for the test that is
neglectable. In the test we can now use a project storage mock to
emulate the meta info system. Later we could use a pregenerated database
file to create a fake project storage.
Task-number: QDS-9766
Change-Id: I16efa28bc4b12181941adecc132084157156daec
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
