refactor: make WG summary view into a task

[jennifer-richards]

This moves the work in the wg_summary_by_area and wg_summary_by_acronym views into the new generate_wg_summary_files_task(). The views are refactored to pass the file through instead of generating it on request.

The old views were used by Night-runner and run nightly. I've made these hourly instead because the task is not terribly expensive and this matches the handling of the WG charter file generation. It's easy to change it to daily, though.

Generating these files is fast enough we could refactor further and generate the files both in a task and in the view instead of doing the file pass-through. For the charter files, we had caching in place that meant we were effectively serving the generated files anyway. For the summary files, there was no such caching so this is more of a change. Unless there's a strong need for it, though, I'd rather keep these views the same.

Fixes https://github.com/ietf-tools/infra-cloud/issues/204

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.93%. Comparing base (187c2c5) to head (6be04dd).
Report is 237 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7529      +/-   ##
==========================================
- Coverage   88.98%   88.93%   -0.06%     
==========================================
  Files         291      295       +4     
  Lines       40717    41235     +518     
==========================================
+ Hits        36233    36672     +439     
- Misses       4484     4563      +79     

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