fix: use BOF states in concluded_groups()

[jennifer-richards]

Fixes #7770 (though database cleanup will also be needed).

This uses ChangeStateGroupEvent states "bof" and "bof-conc" instead of "active" and "concluded" when displaying BOFs on the concluded_groups() view.

This leads to quite a few changes because there seem to be a number of data quality problems. Some that I've noticed:

• aggsrv has no concluded date because its history entry is a GroupEvent rather than a ChangeStateGroupEvent
• netgraph (and other older groups) have ChangeStateGroupEvent records with "active" state rather than "bof"
• ietfgrow has only a "conclude" event
• many groups have only a concluded date

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.77%. Comparing base (c7f6bde) to head (921a928).
Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7771      +/-   ##
==========================================
- Coverage   88.78%   88.77%   -0.01%     
==========================================
  Files         296      296              
  Lines       41320    41337      +17     
==========================================
+ Hits        36687    36698      +11     
- Misses       4633     4639       +6     

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