[TIMOB-8973] iOS: Locking/lock management evaluation

Currently for iOS, we may have some serious lock management problems. It has been mentioned, in particular, that the childLock used for view child add/remove/management could lead to deadlocks from multiple read locks across threads in some situations. Locking is also drastically impacting our speed and ability to perform certain types of operations in iOS (in particular, add/remove). This task is related to, but not dependent upon, TIMOB-6990 (partially complete; [sptramer/timob-6990](https://github.com/sptramer/titanium_mobile/tree/timob-6990)). That task only takes care of locking situations involving contexts.