Summary:
This diff refactors the view update process into two stages:
1. The `reactSubviews` array is set, whose order matches the order of the JS components and shadowView components, as specified by the UIManager.
2. The `didUpdateReactSubviews` method is called, which actually inserts the reactSubviews into the view hierarchy.
This simplifies a lot of the hacks we had for special-case treatment of subviews: In many cases we don't want to actually insert `reactSubviews` into the parentView, and we had a bunch of component-specific solutions for that (typically overriding all of the reactSubviews methods to store views in an array). Now, we can simply override the `didUpdateReactSubviews` method for those views to do nothing, or do something different.
Reviewed By: wwjholmes
Differential Revision: D3396594
fbshipit-source-id: 92fc56fd31db0cfc66aac3d1634a4d4ae3903085
46c02b6ae5