feat: Adds LlamaCpp LLM

[bruvduroiu]

• uses llama-cpp-python as Python bindings for https://github.com/ggerganov/llama.cpp

• refactors semantic_router.utils.function_call.{extract_function_inputs,is_valid_input} into semantic_router.llm.base.BaseLLM class methods (API-based, llama.cpp-based and HF-based LLMs can override this method)

closes #64

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (666b361) 89.03% compared to head (2285771) 91.25%.

Files	Patch %	Lines
semantic_router/llms/llamacpp.py	90.00%	4 Missing ⚠️
semantic_router/llms/base.py	96.77%	1 Missing ⚠️
semantic_router/route.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #96      +/-   ##
==========================================
+ Coverage   89.03%   91.25%   +2.21%     
==========================================
  Files          24       25       +1     
  Lines        1040     1086      +46     
==========================================
+ Hits          926      991      +65     
+ Misses        114       95      -19     

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[jamescalam]

lgtm @bruvduroiu — this is awesome, I'm going to look into tests and will try locally with your notebook, once everything looks good we can merge