feat: rebuild_searchindex task

[jennifer-richards]

Creates a typesense "docs" collection, optionally dropping the old one first, then loads it with index entries for all RFCs.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.42%. Comparing base (15b2abd) to head (7681807).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
ietf/utils/searchindex.py	87.50%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10723   +/-   ##
=======================================
  Coverage   88.42%   88.42%           
=======================================
  Files         331      331           
  Lines       44557    44605   +48     
=======================================
+ Hits        39399    39442   +43     
- Misses       5158     5163    +5     

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