This merges the tempFile and caching tests, which had been updated in
commit ae03ffaffd to attempt other
filesystems than APFS and btrfs.
Instead of adding yet another item to the list (xfs), let's insist by
writing more and flushing the OS buffers. Local testing says that btrfs
usually updates after the first write(), no later than the second, and
that APFS and XFS "just works" now (without the fsync() even).
Pick-to: 6.7
Fixes: QTBUG-123151
Change-Id: I6818d78a57394e37857bfffd17bbe7427307efc4
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
025c45d628