Add unit tests for ExceptionEvaluator, ExceptionEvent, ExceptionHistory, and ExceptionObject models

- Implemented comprehensive unit tests for the ExceptionEvaluator service, covering various scenarios including matching exceptions, environment checks, and evidence references.
- Created tests for the ExceptionEvent model to validate event creation methods and ensure correct event properties.
- Developed tests for the ExceptionHistory model to verify event count, order, and timestamps.
- Added tests for the ExceptionObject domain model to ensure validity checks and property preservation for various fields.

src/Policy/__Tests/StellaOps.Policy.Exceptions.Tests/StellaOps.Policy.Exceptions.Tests.csproj

@@ -0,0 +1,26 @@
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+  <ItemGroup>
+    <ProjectReference Include="../../__Libraries/StellaOps.Policy.Exceptions/StellaOps.Policy.Exceptions.csproj" />
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