pitr: include WAL PVC as a part of clone and backup

[boddumanohar]

When PITR is enabled:

• as a part of Snapshot, we should store WAL PVC's details in Backup Entry
• as a part of clone, we should also clone and restore the WAL PVC

testing

1. create a branch with PITR enabled.
2. clone the branch --> both DATA and WAL PVC are cloned (since WAL is initialised at a separate location)
3. backup the branch --> make sure that both DATA and WAL PVC are cloned
4. setup periodic snapshots --> make sure that both DATA and WAL PVC are getting cloned
5. snapshot retention --> make sure that both the snapshots are getting deleted
6. create a branch from a backupID (similar behaviour as backup) --> the new branch should have both DATA and WAL PVCs