We should add a new compat phase to our pipeline where we run our unittests against our Test projection but instead of the Test projection being generated using the latest CsWinRT, it should be generated with a couple different major CsWinRT versions from past releases. This would allow us to better validate CsWinRT projections generated with older versions against the latest Windows SDK projection and WinRT.Runtime as those can be updated independently and needs to remain compatible.