This was unnecessarily using a bunch of mutexes and atomics, which we can do away with by moving it to our ApplicationDelegate which is always accessed on the main thread.

This should make it easier for me to move towards not queuing events as much, and should also make the code-base slightly more understandable for someone who has done macOS development before (it's a common pattern to put stuff in your app delegate).

• Tested on all platforms changed