Use Rust to accelerate negative sampling

[mdekstrand]

This pushes the negative sampling verification logic into Rust to dramatically speed up sampling, especially for multiple items.

This also introduces a RowColumnSet data structure for fast negative verification.

Closes #720.

[codecov]

Codecov Report

Attention: Patch coverage is 91.03448% with 13 lines in your changes missing coverage. Please review.

Project coverage is 90.45%. Comparing base (12934c9) to head (6c5d58f).
Report is 19 commits behind head on main.

Files with missing lines	Patch %	Lines
src/lenskit/data/matrix.py	87.77%	11 Missing ⚠️
src/lenskit/data/relationships.py	96.36%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #723      +/-   ##
==========================================
- Coverage   90.45%   90.45%   -0.01%     
==========================================
  Files         137      137              
  Lines        9643     9713      +70     
==========================================
+ Hits         8723     8786      +63     
- Misses        920      927       +7     

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