Consider removing the MachineIndependent configuration

https://github.com/search?q=repo%3Adotnet%2Fmsbuild%20MachineIndependentBuild&type=code

From what I know, this configuration is used to create a portable / xcopy msbuild environment. Now that Mono is EOL and VS changing to a rapid release cadence, I don't see much value in keeping this support and the ifdefs that come with, alive.

@rainersigwald opinions?