Update google_sql_database and google_sql_user to not do Read actions when instance is not active

[modular-magician]

This pull request addresses issue hashicorp/terraform-provider-google#7810. If the activation policy is not ALWAYS i.e. the instance is not active, return from the get resource method of "user" and "database". In the API layer if the activation policy is not set the ALWAYS then get resource will throw an error. To avoid breaking terraform plan, updating the getter method to avoid the error during refresh.

With these changes, terraform plan and terraform apply will succeed. If the customer try to update/delete the resource, it will still throw exception as it is not supported for inactive resources.

Release Note Template for Downstream PRs (will be copied)

sql: updated `google_sql_database` and `google_sql_user` so they don't perform Read operations if their associated `google_sql_database_instance` has `activation_policy` set to "NEVER". This avoids triggering API errors while the instance is unavailable.

Derived from GoogleCloudPlatform/magic-modules#11866