Summary:
Fixes an issue introduced in https://github.com/facebook/react-native/pull/15894 that can cause events to be dispatched out of order.
Also reverted `viewTag` moved to optional property as it didn't actually work and makes code more complex.
[iOS] [Fixed] - Fix event ordering when combining coalescable and non-coalescable events
Pull Request resolved: https://github.com/facebook/react-native/pull/24693
Differential Revision: D15279513
Pulled By: shergin
fbshipit-source-id: 3c64aba6d644ea9564572e6de8330b59b51cf4a9