Add sample redis rag application

…vements

1. Fix trace_id/span_id type conversion across all instrumentations
   - Convert OpenTelemetry integer IDs to strings before upload calls
   - Standardize all signatures to use 4-parameter format consistently
   - Fix OpenAI config signature mismatch (was expecting 3 params, using 4)

2. Improve code readability (Issue #4 from PR review)
   - Extract helper methods to reduce complex nested if/else blocks
   - Use descriptive variable names (arg_index, content_item vs i, arg)
   - Apply consistent patterns across VertexAI and Google GenAI instrumentations
   - Maintain both async and sync versions with shared logic

3. Fix VertexAI ChatSession model name extraction
   - Add support for getting model name from ChatSession._model reference
   - Ensures send_message spans show correct model instead of "unknown"

All changes maintain backward compatibility and pass linting checks.

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Co-Authored-By: Claude <noreply@anthropic.com>