feat: [CDE-585]: Support creation and attaching of persistent disks

[vikyathharekal]

Description

1. Create Disk
   • Create (if required) and attach the persistent disk to the VM.
   • Wait for the disk to be created and then initiate instance creation.
   • Pass storage type (example: "pd-balanced")
   • storage_identifier supports a comma-separated list of identifiers, to support 2 separate disks (1 for gitspace and 1 for docker) in the future.
2. Delete Disk
   • Delete the disk on Delete Gitspace (StorageCleanupType.DELETE).
   • Disk would retained in case of Stop Gitspace (StorageCleanupType.DETACH).
   • If the disk needs to be deleted, wait for instance deletion to complete and then hit the delete disk API.
   • Add storage_identifier in instance info (This will be sent in the destroy request to identify the disk and delete it)
   • Pass StorageCleanupType in VMCleanupRequest
3. Skip CDE VMs from cleanup by setting "retain": true label

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[raghavharness]

LGTM