Allow Lookup of Serverless usage Policy ID in dab yaml

[brookpatten]

Asset Bundle Yaml allows lookups of alert, cluster_policy, cluster, dashboard, instance_pool, job, metastore, notification_destination, pipeline, query, service_principal, and warehouse.

https://docs.databricks.com/aws/en/dev-tools/bundles/variables#retrieve-an-objects-id-value

It does not currently allow lookup of serverless usage_policy_id, therefore users have to manage differing policies by pasting guids into their dab yaml. It would be cleaner if we could reference a policy by name and deploy the named policy to different workspaces, then use a lookup function to reference it.