Added ability to test distributed tracing functionality.

[LarryOsterman]

Fixes #2769 - Adds ability to easily test distributed tracing.

Also adds a test example for KeyVault Secrets APIs.

This PR introduces a new azure_core_test API named assert_instrumentation_information whose purpose is to ensure that the distributed tracing information is correctly generated for a given service client implementation.

The API takes three pieces of information: A capture which creates a service client with a provided distributed tracing TracerProvider, a capture which actually performs the test and an InstrumentationInformation structure which describes the service calling the API and the particular service client APIs which are expected to have been called during the test.

It then analyzes the actual traces generated during the test and verifies that the expected service client calls were made and that the expected distributed tracing attributes have been generated.

[Copilot]

Pull Request Overview

This PR adds comprehensive distributed tracing testing functionality to the Azure SDK for Rust, allowing developers to easily verify that their client libraries generate correct telemetry data. The implementation includes a new test framework for instrumentation validation and demonstrates its usage with KeyVault Secrets APIs.

• Introduces test_instrumentation_for_api function for automated tracing verification
• Adds structured data types for defining expected instrumentation behavior
• Provides test examples across multiple Azure service clients

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
sdk/core/azure_core_test/src/tracing.rs	Core implementation of the tracing test framework with helper types and validation logic
sdk/keyvault/azure_security_keyvault_secrets/tests/secret_client.rs	Example test demonstrating distributed tracing verification for KeyVault operations
sdk/core/azure_core_opentelemetry/tests/telemetry_service_macros.rs	Additional test examples for HTTP and function-level tracing scenarios
sdk/core/azure_core/src/http/pipeline.rs	Comment relocation for better code organization
sdk/keyvault/assets.json	Test asset version update
sdk/core/azure_core_opentelemetry/assets.json	Test asset version update

[heaths]

I think taking a capture that passes the InstrumentationInformation would be much easier to use for test authors. Happy to debate it further, though.