feat: llm reranker pipeline

[LongxingTan]

Description

This PR ...

Checklist

• Linked issues (if existing)
• Amended changelog.md for large changes (and added myself there as contributor)
• Added/modified tests
• Used pre-commit hooks when committing to ensure that code is compliant with hooks. Install hooks with pre-commit install.
  To run hooks independent of commit, execute pre-commit run --all-files

Thank you for joining. Have fun coding!

[codecov]

Codecov Report

Attention: Patch coverage is 62.16216% with 28 lines in your changes missing coverage. Please review.

Project coverage is 51.38%. Comparing base (fb6f376) to head (40f7e79).

Files	Patch %	Lines
src/retrievals/losses/token_loss.py	40.90%	13 Missing ⚠️
src/retrievals/models/rerank.py	29.41%	12 Missing ⚠️
src/retrievals/data/collator.py	91.17%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #61      +/-   ##
==========================================
+ Coverage   50.93%   51.38%   +0.45%     
==========================================
  Files          26       27       +1     
  Lines        2252     2314      +62     
==========================================
+ Hits         1147     1189      +42     
- Misses       1105     1125      +20     

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