Alloydb crr secondary instance

[modular-magician]

To Create a Secondary Instance inside a secondary cluster, set the instance_type to point to the cluster_type of the associated secondary cluster & set lifecycle.ignore_changes = [instance_type]
Avoid setting instance_type = "SECONDARY", as promoting a secondary cluster to a primary cluster also modifies the instance_type of the associated secondary instance

  instance_type = google_alloydb_cluster.<secondary_cluster_name>.cluster_type
  lifecycle {
    ignore_changes = [instance_type]
  }

Release Note Template for Downstream PRs (will be copied)

alloydb: added "SECONDARY" as an additional option for `instance_type` field in `google_alloydb_instance` to support creation of secondary instance inside a secondary cluster. 

alloydb: added "deletion_policy" to `google_alloydb_cluster` to allow force-destroying instances along with their cluster. This is necessary to delete secondary instances, which cannot be deleted otherwise.

alloydb: increased default timeout on `google_alloydb_instance` to 120m from 40m

Derived from GoogleCloudPlatform/magic-modules#9203

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