Implement Linux compatible live tester

[TorjeAmundsen]

The current implementation of the live output tester relies on a lot of Windows-specific features, so it does not currently work on Linux.

I am not implementing Linux support for this lol, but someone else can feel free to. It was already a pain to do on Windows and I don't have Linux on any machine.

[TorjeAmundsen]

I have annotated windows-specific features with [SupportedOSPlatform("windows")] now, so it's easier to find what needs work to be Linux-compatible.

(It's quite a few things, sorry)