Remove OPRF IPA code

[akoshelev]

As we migrated everything to Hybrid, the old code is just a copy-paste and carries some dead weight we should avoid. There is a branch oprf-ipa that has everything if we ever need to pick up this code again.

Unfortunately we made quite a bit of shortcuts and there is currently no benchmark code for Hybrid

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.08%. Comparing base (afb5e48) to head (7fecafc).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
ipa-core/src/bin/report_collector.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1523      +/-   ##
==========================================
- Coverage   93.08%   92.08%   -1.01%     
==========================================
  Files         237      220      -17     
  Lines       44209    38237    -5972     
==========================================
- Hits        41153    35211    -5942     
+ Misses       3056     3026      -30     

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