FCM's swizzling of the user notification center currently swizzles only one of the two optional delegate methods (userNotificationCenter:willPresentNotification:withCompletionHandler:), but not the other (userNotificationCenter:didReceiveNotificationResponse:withCompletionHandler:).
The didReceiveNotificationResponse, if implemented by the delegate, is the sole receiver of all user action on a notification, including simply tapping on the notification itself. Prior to this change, if the developer had implemented didReceiveNotificationResponse, then FCM would not be able to collect this event for analytics.
Additionally, I changed the logic in FIRMessagingRemoteNotificationsProxy to check whether these methods are actually implemented before swizzling them. It was always swizzling, which meant it was adding an implementation if the method didn't exist. This would confuse iOS into thinking the developer did implement these methods and NOT fall back to delivering the notifications to the application delegate.
With this change, if the developer did not implement these methods, then FCM will not swizzle those methods. That keeps the behavior true to what the developer intended.
This removes the `FIRMessaging_FAIL` macro which was using `__builtin_trap()`, and replaced with `NSAssert` calls. These `NSAssert` calls may not get called in release builds, and so we also log them with FIRLogger error messages.
The RMQ database open error result code is now parsed and included in the error message to help us identify causes for #199 .
* Remove mostly unused code from FIRMessagingLogger
This cleans up some left-over old logging logic from before we moved to FIRLogger in Firebase Core. We no longer need this logging functionality.
* Delete FIRMessagingConfig.{h,m}
We no longer need a config class to store an unused log level filter (that filter is no longer needed).
Chen Liang