Include the ExitCode in the error message (#17663)

.azure/pipelines/ci.yml

...ools/Microsoft.dotnet-openapi/src/Commands/BaseCommand.cs

...ools/Microsoft.dotnet-openapi/test/OpenApiAddFileTests.cs

...s/Microsoft.dotnet-openapi/test/OpenApiAddProjectTests.cs

...Tools/Microsoft.dotnet-openapi/test/OpenApiAddURLTests.cs

...ools/Microsoft.dotnet-openapi/test/OpenApiRefreshTests.cs

...Tools/Microsoft.dotnet-openapi/test/OpenApiRemoveTests.cs

src/Tools/Microsoft.dotnet-openapi/test/OpenApiTestBase.cs