Feature 10509: Add support for scaling KDUs

- Add kdu-resource-profile: Profile that references to a particular
resource of a KDU (i.e. deployment/statefulset/etc. of a KDU).
- Add kdu-resource-delta: Delta list for the scaling-in and -out of a
KDU.
- Add vnfd_sol006_k8s_scale.yaml under tests/examples: Descriptor
example.

Change-Id: I6b159341216a54776049da4f6145f0c3e030ff12
Signed-off-by: David Garcia <david.garcia@canonical.com>
(cherry picked from commit b8c59539)