BREAKING CHANGE: WinObjC has been refactored to move off fibers

[nicholasgerard-msft]

WinObjC has been refactored to move off fibers and run the iOS main run loop and UI tasks collaboratively on the application’s primary ASTA (UI) thread. This was done in order to plumb various Windows PLM events to WinObjC; in order to accomplish this, we needed a single thread model. Additionally, our previous implementation of hand-rolled fibers had a lot of known limitations. Please let us know if you run into any related issues using the newest release of the bridge.