Transform BubbleEvent and DirectEvent into DirectEventHandler and BubblingEventHandler

Summary:
It appears that `(e: BubblingEvent<T>) = mixed` exists only in given context and it's pointless to keep in this way. It could be simplified to `BubblingEventHandler<T>` without any negative consequences and that's the motivation of this diff.

The only tradeoff of this decision is leaving an opportunity to declare Bubbling/Direct event in the top of the file bc then analysing the code becomes much more difficult. However, it's not used anywhere so it's not a problem now and probably any time.

Also, changes the names to `DirectEventHandler` and `BubblingEventHandler` which are more related to current state. The names were updated in many places in code.

Reviewed By: rubennorte

Differential Revision: D16054571

fbshipit-source-id: 741d075eb46b80bac8eb73a6b30fc0b448cb3902

Libraries/Components/Picker/AndroidDialogPickerNativeComponent.js

@@ -12,7 +12,11 @@
 
 import {requireNativeComponent} from 'react-native';
 
-import type {DirectEvent, Int32, WithDefault} from '../../Types/CodegenTypes';
+import type {
+  DirectEventHandler,
+  Int32,
+  WithDefault,
+} from '../../Types/CodegenTypes';
 import type {TextStyleProp} from '../../StyleSheet/StyleSheet';
 import type {ColorValue} from '../../StyleSheet/StyleSheetTypes';
 import type {NativeComponent} from '../../Renderer/shims/ReactNative';
@@ -39,7 +43,7 @@ type NativeProps = $ReadOnly<{|
   selected: WithDefault<Int32, 0>,
 
   // Events
-  onSelect?: (event: DirectEvent<PickerItemSelectEvent>) => void,
+  onSelect?: DirectEventHandler<PickerItemSelectEvent>,
 |}>;
 
 type ReactPicker = Class<NativeComponent<NativeProps>>;