added custom_rag_agent demo to gen-ai-agents

[luigisaetta]

This pull request is to add to the repository all the code for a Custom RAG Agent demo.

The demo is based on:

• OCI Generative AI Service (Llama 3.3 70B)
• OCI APM for tracing
• Python
• LangGraph
• Langchain

Elements of innovation:

• OCI GenAI/LangGraph integration
• Usage of Llama 3.3 as a reranker, with afine-tuned prompt
• INtegration with OCI APM for Observability

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[luigisaetta]

ok, it was a mistake in local github config. Closed and submitted a new PR