Add back support for lazy tabs and use removeClippedSubviews (#3538)

* Lazy initialization of tabs and move contents off-screen when not active

* Make subview clipping and lazy both configurable

* Record snapshots again

* Update type definition

* Remove unused log

flow/react-navigation.js

@@ -833,6 +833,8 @@ declare module 'react-navigation' {
   declare type _TabNavigatorConfig = {|
     ...NavigationTabRouterConfig,
     ..._TabViewConfig,
+    lazy?: boolean,
+    removeClippedSubviews?: boolean,
     containerOptions?: void,
   |};
   declare export function TabNavigator(