Change Animated's Flow Type to require useNativeDriver be explicit

Summary:
We found that many callsites existed that could be using the native driver, but weren't. In order to help people use it when appropriate and eventually switch the default, we are requiring that useNativeDriver is explicit, even when set to false.

For now, we are changing the flow type to turn this on at Facebook, but aren't making this a runtime warning until we have a bit more confidence in our plans so that we don't churn the community.

Reviewed By: mdvacca

Differential Revision: D16611301

fbshipit-source-id: dfa8536786fc949f0239118a9e0936b268b1081d

Libraries/Animated/src/animations/Animation.js

@@ -18,7 +18,7 @@ export type EndCallback = (result: EndResult) => void | Promise<void>;
 
 export type AnimationConfig = {
   isInteraction?: boolean,
-  useNativeDriver?: boolean,
+  useNativeDriver: boolean,
   onComplete?: ?EndCallback,
   iterations?: number,
 };