[Infra] Refactor EventSource tests

[martincostello]

Complements open-telemetry/opentelemetry-dotnet-contrib#3864.

Changes

Refactor EventSource validation to improve assertions.

Example assertion failure before:

    System.Exception : Method 'AspNetInstrumentationEventSource.RequestIsFilteredOut' is implemented incorrectly.
    ---- System.InvalidOperationException : Sequence contains no matching element

Example assertion failure after:

    EventSource 'OpenTelemetry.Instrumentation.AspNet.Implementation.AspNetInstrumentationEventSource' has event ID validation error(s):
    Duplicate EventId 4: methods 'InvalidConfigurationValue' and 'NullActivity' share the same ID.
    Event NullActivity is givien event ID 4 but 5 was passed to WriteEvent.
    Event NullActivity has ID 4 which is already in use.
    Event NullActivity (with ID 4) has the same task/opcode pair as event InvalidConfigurationValue (with ID 4).

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.23%. Comparing base (28dc317) to head (9c6c9d4).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6896      +/-   ##
==========================================
- Coverage   87.30%   87.23%   -0.08%     
==========================================
  Files         263      263              
  Lines       12387    12387              
==========================================
- Hits        10815    10806       -9     
- Misses       1572     1581       +9     

Flag	Coverage Δ
unittests-Project-Experimental	86.20% <ø> (-1.06%)	⬇️
unittests-Project-Stable	86.16% <ø> (-0.98%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.
see 5 files with indirect coverage changes

[Copilot]

Pull request overview

This PR refactors the EventSource test infrastructure to improve error reporting and validation. It replaces the old event listener-based testing approach with a more robust validation method using EventSource.GenerateManifest with strict mode, which performs IL-level inspection to verify that WriteEvent calls match their [Event] attributes. The refactoring also adds explicit duplicate event ID detection.

Changes:

• Replaced the old MethodsAreImplementedConsistentlyWithTheirAttributes method with a new ValidateEventSourceIds method that provides clearer error messages
• Added comprehensive tests for the helper class itself to validate various error scenarios
• Updated all EventSource test files across multiple projects to use the new validation approach and corrected test method naming (EventSourceTest → EventSourceTests)

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/OpenTelemetry.Tests/Shared/TestEventListener.cs	Added CA1812 warning suppression for unused internal class
test/OpenTelemetry.Tests/Shared/EventSourceTestHelper.cs	Complete refactor: replaced old validation logic with GenerateManifest-based approach and duplicate ID detection
test/OpenTelemetry.Tests/EventSourceTests.cs	Updated to use new ValidateEventSourceIds method and fixed test method name
test/OpenTelemetry.Tests/EventSourceTestHelperTests.cs	New file: comprehensive tests for the EventSourceTestHelper validation logic
test/OpenTelemetry.Extensions.Propagators.Tests/EventSourceTests.cs	Updated to use new ValidateEventSourceIds method and fixed test method name
test/OpenTelemetry.Extensions.Hosting.Tests/EventSourceTests.cs	Updated to use new ValidateEventSourceIds method and fixed test method name
test/OpenTelemetry.Exporter.Zipkin.Tests/EventSourceTests.cs	Updated to use new ValidateEventSourceIds method and fixed test method name
test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/EventSourceTests.cs	Updated to use new ValidateEventSourceIds method and fixed test method name
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/EventSourceTests.cs	Updated to use new ValidateEventSourceIds method and fixed test method names (3 tests)
test/OpenTelemetry.Api.Tests/EventSourceTests.cs	Updated to use new ValidateEventSourceIds method and fixed test method name

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[cijothomas]

nice!
At some point in future, we should be able to weaver-generate these code from a schema.