feat: Add LiteLLM embedder and reranker support

[ItsRoy69]

Summary

Implements LiteLLM unified interface support for embeddings and reranking as requested in Closes #4937.

Key Features

• Unified interface for multiple embedding providers via LiteLLM
• Support for batch processing and async operations
• Usage tracking and metadata extraction

(If applicable, issue number: #____)

Type of change

• [ ] Bug fix
• [x] New feature
• [ ] Breaking change
• [ ] Improvement
• [ ] Model update
• [ ] Other:

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Checklist

• [x] Code complies with style guidelines
• [x] Ran format/validation scripts (./scripts/format.sh and ./scripts/validate.sh)
• [x] Self-review completed
• [ ] Documentation updated (comments, docstrings)
• [ ] Examples and guides: Relevant cookbook examples have been included or updated (if applicable)
• [x] Tested in clean environment
• [x] Tests added/updated (if applicable)

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Additional Notes

Add any important context (deployment instructions, screenshots, security considerations, etc.)

[dotmobo]

Nice thanks !