Cost Explorer API (13/n): 4h spike of not yet specified work to drive cost attribution goal

[consideRatio]

I think its a pre-optimization to try to specify and prioritize what to be done after the following planned work is completed:

• Cost Explorer API (8/n): allow aws-ce-grafana-backend software to be traitlets configurable (in a "chart passthrough" manner) #4788
• Cost Explorer API (9/n): adopt strategy for total costs #4787
• Cost Explorer API (10/n): adopt strategy for total cost per hub #4784
• Cost Explorer API (11/n): adopt strategy for total component attributed costs #4785
• Cost Explorer API (12/n): adopt strategy for component attributed costs per hub #4786

At the same time, if we want to give cost attribution goal a high prio while avoiding unplanned work, and we struggle to define what makes sense to do after the sequence above, we risk ending up blocking ourselves. We could invest time to plan work after the sequence of work above that doesn't make sense after the sequence of work above is done, or we could end up not driving effort into cost attribution because we haven't planned something.

This issue is meant to mitigate that situation.

Definition of done

• Work up to 4h in a way to drive the cost attribution effort following the completion of previous issues.

[consideRatio]

I did some cleanup things, going for a close.