kms: testing: add KMS test dummy registry
kms: testing: add KMS test dummy registry

Add registry similar to the providers one. This allows testers to
add and use GetKMSTestDummy() to create stripped down provider
instances suitable for use in unit tests.

Signed-off-by: Marcel Lauhoff <71ffe8e889bf8a669a25bf46f8e88e7fab585e83@suse.com>

ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi