List VMs on a Datastore

[OpenNebulaSupport]

Description
List all VMs deployed on a specific Datastore from the CLI or Sunstone interface.

Use case
Currently there's no way of doing this in a direct manner, instead it's necessary to either check each VM individually or run custom scripts from CLI. This should be similar as how it's possible to view all images on a Image DS, from the "Images" tab.

Interface Changes
From Sunstone, it would be interesting to have something like "Storage>Datastores>Datastore>VMs", so there's a tab on each system datastore that shows a list of all currently deployed VMs on it.
From CLI, it could be implemented on the onedatastore command, for example with something like onedatastore show DS_ID --vms.

Additional Context

Progress Status

• Code committed
• Testing - QA
• Documentation (Release notes - resolved issues, compatibility, known issues)