This PR upgrades RNX to target RNW 0.72, along with several fixes to
make that possible.
Changes:
* RNX project and examples updated (dev) dependency to target RN/RNW 0.72
* RNX now default targets WinUI 2.8.0 (as per RNW 0.72)
* Improved Codegen to understand environment variables in winmd paths
* Adds the paths of winmd's used into codegened files for future debugging
* Removes the "source line" comments in the codegen that contain local dev paths
* RNX project will now run codegen before building if it detects that the version of WinUI being requested doesn't match the version last used to run the codegen
* RNX project updated to make sure it can still be built against older supported versions of RNW
* Pipeline fixes to make sure we're testing against the correct versions of everything
* Removal of (now) unnecessary SetupAppForNuGet script as apps will target whichever WinUI RNW targets
* Added `yarn test` for example and cli app builds
Closes#260
Jon Thysell
Alexander Sklar