fix: use area-acronym-at-the-time in proceedings

[russhousley]

When generating IETF meeting proceedings, use the Area Acronym for each WG at the time of the meeting. Fixes #7706.

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 88.79%. Comparing base (187c2c5) to head (4851457).
Report is 341 commits behind head on main.

Files	Patch %	Lines
ietf/meeting/views.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7723      +/-   ##
==========================================
- Coverage   88.98%   88.79%   -0.19%     
==========================================
  Files         291      296       +5     
  Lines       40717    41331     +614     
==========================================
+ Hits        36233    36701     +468     
- Misses       4484     4630     +146     

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[jennifer-richards]

Looks to me like it's working. It's adding 15-20% more queries to the proceedings calculation (for 119, it adds about 500 to the already very large query count of 2840 when rendering the page).

I suspect we can improve the cost of this change, but better to look at it in the big picture than to dig deep on it now.