.Net: Added traces for Agent invocations

[dmytrostruk]

Motivation and Context

Resolves: #10174

This PR instruments Agent invocation operation with traces and adds an example with tracing enabled using Console and Application Insights.

Trace operation and attribute names are based on the work in following PR about adding AI Agent Semantic Convention to OpenTelemetry (currently in-progress): open-telemetry/semantic-conventions#1739.

Examples from Application Insights:

End-to-end transaction:

Traces:

Trace attributes related to Agent:

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄