clean up the nightsum and prenight Times Square notebooks by updating schedview to support them better

done in github

This issue has corresponding pull requests on several repositories:

• rubin_scheduler branch tickets/https://rubinobs.atlassian.net/browse/PREOPS-5361#icft=PREOPS-5361

• rubin_sim branch tickets/https://rubinobs.atlassian.net/browse/PREOPS-5360#icft=PREOPS-5360

• schedview branch tickets/https://rubinobs.atlassian.net/browse/PREOPS-5360#icft=PREOPS-5360

• schedview_notebooks branch tickets/https://rubinobs.atlassian.net/browse/PREOPS-5360#icft=PREOPS-5360

The nightsum and Times Square notebooks currently do some awkward things to be able to call the relevant schedview support functions. Refactor schedview so this isn’t necessary.