feat: Part 1 - Add RAG Embedding Interface

[ishaansehgal99]

Reason for Change:
This series of PR will integrate llamaindex RAG service for Kaito.

This first PR introduces the Embedding Model Interface and two classes that implement it huggingface_local and huggingface_remote. These allows users to specify both local and remote HuggingFace models for text embeddings.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.73%. Comparing base (5c30038) to head (5c59427).
Report is 30 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #628      +/-   ##
==========================================
- Coverage   58.18%   54.73%   -3.46%     
==========================================
  Files          30       34       +4     
  Lines        2987     3234     +247     
==========================================
+ Hits         1738     1770      +32     
- Misses       1149     1358     +209     
- Partials      100      106       +6     

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