.NET: Add AIClient HTTP Traffic Tracing sample with logging capabilities

[Vijay-Nirmal]

Motivation and Context

fix: #632

Description

This PR add a sample showing how to enable HTTP request/response logging for LLM calls (including request/response bodies) for any AIClient.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This PR adds a new sample demonstrating HTTP request/response logging capabilities for AIClient implementations. The sample shows developers how to enable detailed HTTP traffic tracing including request/response bodies, headers, and URLs for debugging and troubleshooting purposes.

• Adds a new AIClientHttpTrafficTracing sample in the Observability folder
• Demonstrates configuration of ClientLoggingOptions for Azure OpenAI clients
• Includes comprehensive documentation with security warnings about logging sensitive data

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 15 comments.

File	Description
dotnet/samples/GettingStarted/Observability/AIClientHttpTrafficTracing/README.md	Documentation explaining HTTP traffic logging setup, prerequisites, security considerations, and usage instructions
dotnet/samples/GettingStarted/Observability/AIClientHttpTrafficTracing/Program.cs	Sample code demonstrating ClientLoggingOptions configuration with Azure OpenAI and dependency injection
dotnet/samples/GettingStarted/Observability/AIClientHttpTrafficTracing/AIClientHttpTrafficTracing.csproj	Project file with necessary dependencies for the sample
dotnet/agent-framework-dotnet.slnx	Solution file updated to include the new sample project