Simplified event registration

Summary:
Our events all follow a common pattern, so there's no good reason why the configuration should be so verbose. This diff eliminates that redundancy, and gives us the freedom to simplify the underlying mechanism in future without further churning the call sites.

Examples/UIExplorer/UIExplorerUnitTests/RCTEventDispatcherTests.m

@@ -64,7 +64,7 @@
   _eventDispatcher = [[RCTEventDispatcher alloc] init];
   ((id<RCTBridgeModule>)_eventDispatcher).bridge = _bridge;
 
-  _eventName = @"sampleEvent";
+  _eventName = RCTNormalizeInputEventName(@"sampleEvent");
   _body = @{ @"foo": @"bar" };
   _testEvent = [[RCTTestEvent alloc] initWithViewTag:nil
                                            eventName:_eventName
@@ -125,7 +125,7 @@
 
 - (void)testDifferentEventTypesDontCoalesce
 {
-  NSString *firstEventName = @"firstEvent";
+  NSString *firstEventName = RCTNormalizeInputEventName(@"firstEvent");
   RCTTestEvent *firstEvent = [[RCTTestEvent alloc] initWithViewTag:nil
                                                            eventName:firstEventName
                                                                 body:_body];