[aurora] Add support for RDS Aurora

[pflorek]

Feature scope

AWS/RDS

Describe your suggested feature

Hey together,

I would like to monitor Aurora. The CDK implementation, underlying CFN resource and metrics/namespace is almost same to RDS (sure some won't apply).

Currently, I'm just type casting IServerlessCluster, which feels brittle: cluster as unknown as rds.IDatabaseCluster

[voho]

Thanks for the suggestion. Will start with the implementation soon. Any aurora-specific metrics you would like not to be missed?

[zqumei0]

I figured I would take a stab at this since I didn't see anything yet. Happy to get some feedback on implementation of this. Most of the metrics are the same but ServerlessCluster had serverless specific metrics, so I used the same metrics factory as RDS but a separate monitor to pull different metrics. I only added Serverless Database Capacity cluster metric and a corresponding alarm. Need to look into more metrics that are good to have. Let me know if either of you have any thoughts!