Preserve PV's AZ info when snapshotting and restoring PVs.

- Read PV's AZ info from fault-domain label of the PV object for snapshotting.
- Store PV's AZ info in the VolumeInfo.
- Add tests for reading the label from the PV object.
- Remove availability zone validation in AWS and GCP BlockStorageAdaptor.
- Add volumeAZ as a parameter to methods in the BlockStorageAdapter interface.
- Get AZ from VolumeInfo when restoring PV snapshot.
- Remove references to PV availability zone in docs.

Signed-off-by: Ashish Amarnath <ashish.amarnath@gmail.com>

examples/aws/00-ark-config.yaml

@@ -21,7 +21,6 @@ metadata:
 persistentVolumeProvider:
   aws:
     region: <YOUR_REGION>
-    availabilityZone: <YOUR_AVAILABILITY_ZONE>
 backupStorageProvider:
   bucket: <YOUR_BUCKET>
   aws:

examples/gcp/00-ark-config.yaml

@@ -21,7 +21,6 @@ metadata:
 persistentVolumeProvider:
   gcp:
     project: <YOUR_PROJECT>
-    zone: <YOUR_ZONE>
 backupStorageProvider:
   bucket: <YOUR_BUCKET>
   gcp: {}