This extends the existing "ephemeral volume" tests to also cover
generic ephemeral inline volumes. They get instantiated for all
drivers (CSI and others) which support persistent volume provisioning,
for several different filesystems.
Configuring the number of inline volumes via a flag with a computed
name had been identified as problematic before and now gets removed
because re-using the tests as a stress test with a higher number of
volumes should be added and configured separately.
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