[alloydb] [enhancement] manage switchover status

[baran81]

Describe the bug
if the cluster switchover to secondary terraform state is invalid and you cant change parameters and size of the cluster.

To Reproduce
create a cluster with secondary
do switchover via "gcloud alloydb clusters switchover"
try terraform plan

Expected behavior
have a flag to manage the configuration also during a switchover shenario

[juliocc]

This is not something specific to the Fabric alloydb module. If you modify a Terraform-managed resource outside Terraform, you will have to reconcile the state manually.

[ludoo]

Reopening, @simonebruzzechesse has a solution in mind and this is just for him to log the requirements.