Enabling GCController.shouldMonitorBackgroundEvents to read background events
for MFi controllers before receiving the first GCControllerDidConnectNotification
is apparently a no-go on macOS (12.3.1 for me), and would crash on attempt.
Apple's documentation is... not great, and doesn't point this out.
This waits for IOS_AddMFIJoystickDevice() to get called down the chain from GCControllerDidConnectNotification, and enables GCController.shouldMonitorBackgroundEvents
if it hadn't been already.
On iOS and tvOS, GCController.shouldMonitorBackgroundEvents is ignored, so
there's no need to check their versions.
