MTP Code Coverage different default behaviour to runsettings

[tonyhallett]

Describe the issue or suggestion

https://github.com/dotnet/docs/blob/main/docs/core/testing/microsoft-testing-platform-extensions-code-coverage.md

Perhaps an additional note that there is a difference in the default behaviour for IncludeTestAssembly.

https://github.com/microsoft/codecoverage/blob/main/docs/configuration.md