Improve Python scores API

[PeterJCLaw]

Currently it's not especially ergonomic to get the scores for a given match or a given team from within the Python API. (It's actually easier in the HTTP API!).

It would be great if this was easier.

Prior art for consideration:

• sr.comp.http.query_utils.get_scores
• Plot tooling in the SR2021 compstate:
  • https://github.com/srobo/sr2021-comp/blob/master/plot.py#L14
  • https://github.com/srobo/sr2021-comp/blob/master/plot-periods.py#L17