Fix promises on iOS to no longer wrap values in Arrays

Summary:
public
In https://github.com/facebook/react-native/commit/9baff8f437eee49f8ab0e6f433bf86466ca16662#diff-8d9841e5b53fd6c9cf3a7f431827e319R331, I incorrectly assumed that iOS was wrapping promises in an extra Array.  What was really happening is that all the callers were doing this.  I removed the wrapping in the callers and the special case handling MessageQueue.

Now one can pass whatever object one wants to resolve and it will show properly in the resolve call on the js side.  This fixes issue https://github.com/facebook/react-native/issues/5851

Reviewed By: nicklockwood

Differential Revision: D2921565

fb-gh-sync-id: 9f81e2a87f6a48e9197413b843e452db345a7ff9
shipit-source-id: 9f81e2a87f6a48e9197413b843e452db345a7ff9

Libraries/Utilities/MessageQueue.js

@@ -324,11 +324,7 @@ class MessageQueue {
             method,
             args,
             (data) => {
-              // iOS always wraps the data in an Array regardless of what the
-              // shape of the data so we strip it out
-              // Android sends the data back properly
-              // TODO: Remove this once iOS has support for Promises natively (t9774697)
-              resolve(Platform.OS == 'ios' ? data[0] : data);
+              resolve(data);
             },
             (errorData) => {
               var error = createErrorFromErrorData(errorData);