[FEATURE] Add DocumentDB Elastic Metrics Support

[Bruc3Stark]

Is there an existing issue for this?

• I have searched the existing issues

Feature description

Now it looks like YACE only supports AWS/DocDB namespace (alias: "docdb"), it would be great if the AWS/DocDB-Elastic namespace can be supported.

What might the configuration look like?

- type: AWS/DocDB-Elastic
  regions:
    - us-west-2
  metrics:
    - name: PrimaryInstanceFreeableMemory
      statistics: [Average]

Anything else?

No response