Adds V3 API samples for the disk-config extension

Adds api sample tests and and api samples for the
disk-config extension

Partially implements blueprint v3-api-unittests
Partially implements blueprint v3-api-specification

Change-Id: Ic5c1e4d4e8c6edf3fceef456a79c1f5b79a3b5aa
Merge "Adds V3 API samples for the disk-config extension"