XUnit test project not part of Visual Studio solution PowerShell.sln -> make XUnit runable from within VS test explorer #7253

Because xunit tests are running now on Windows and not just Linux only, it would make sense to add it to Powershell.sln solution file.
However, this does not work out of the box and needs some time to figure out how to adapt the csproj for that (it does not work out of the box with the upgrade that VS suggests). Any pointers on that?
I have a working prototype in my branch here, will open a PR