### Description

Currently some code in RDS Operators use boto waiters and some uses a custom `_await_status`, the former is preferred over the later (waiters are vetted code provided by the boto sdk, they have features like exponential backoff, etc). See [this discussion thread](https://github.com/apache/airflow/pull/27076#discussion_r997325535) for more details/context.

### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

_create_db_instance(self.hook)
        self.hook.conn.stop_db_instance(DBInstanceIdentifier=DB_INSTANCE_NAME)
        result_before = self.hook.conn.describe_db_instances(DBInstanceIdentifier=DB_INSTANCE_NAME)
        status_before = result_before["DBInstances"][0]["DBInstanceStatus"]
        assert status_before == "stopped"
        start_db_instance = RdsStartDbOperator(
            task_id="test_start_db_instance", db_identifier=DB_INSTANCE_NAME
        )
        _patch_hook_get_connection(start_db_instance.hook)
        start_db_instance.execute(None)
        result_after = self.hook.conn.describe_db_instances(DBInstanceIdentifier=DB_INSTANCE_NAME)
        status_after = result_after["DBInstances"][0]["DBInstanceStatus"]
        assert status_after == "available"
    @mock_rds
    def test_start_db_cluster(self):
        _create_db_cluster(self.hook)
        self.hook.conn.stop_db_cluster(DBClusterIdentifier=DB_CLUSTER_NAME)
        result_before = self.hook.conn.describe_db_clusters(DBClusterIdentifier=DB_CLUSTER_NAME)
        status_before = result_before["DBClusters"][0]["Status"]
        assert status_before == "stopped"
        start_db_cluster = RdsStartDbOperator(
            task_id="test_start_db_cluster", db_identifier=DB_CLUSTER_NAME, db_type="cluster"
        )
        _patch_hook_get_connection(start_db_cluster.hook)
        start_db_cluster.execute(None)
        result_after = self.hook.conn.describe_db_clusters(DBClusterIdentifier=DB_CLUSTER_NAME)
        status_after = result_after["DBClusters"][0]["Status"]
        assert status_after == "available"