Remove unnecessary Event and CustomEvent polyfills (#50495)

Summary:
Pull Request resolved: #50495

Changelog: [internal]

This migrates the last remaining usages of these polyfills to the built-in classes.

Reviewed By: yungsters

Differential Revision: D67828652

fbshipit-source-id: 5ff039d7413aed49d882ff03e722531cdd195488

Author: rubennorte

packages/react-native/Libraries/Events/CustomEvent.js

@@ -8,14 +8,14 @@
  * @flow strict-local
  */
 
+import typeof CustomEvent from '../../src/private/webapis/dom/events/CustomEvent';
 import typeof BatchedBridge from '../BatchedBridge/BatchedBridge';
 import typeof legacySendAccessibilityEvent from '../Components/AccessibilityInfo/legacySendAccessibilityEvent';
 import typeof TextInputState from '../Components/TextInput/TextInputState';
 import typeof ExceptionsManager from '../Core/ExceptionsManager';
 import typeof RawEventEmitter from '../Core/RawEventEmitter';
 import typeof ReactFiberErrorDialog from '../Core/ReactFiberErrorDialog';
 import typeof RCTEventEmitter from '../EventEmitter/RCTEventEmitter';
-import typeof CustomEvent from '../Events/CustomEvent';
 import typeof {
   createPublicInstance,
   createPublicRootInstance,
@@ -99,7 +99,7 @@ module.exports = {
     return require('../Core/RawEventEmitter').default;
   },
   get CustomEvent(): CustomEvent {
-    return require('../Events/CustomEvent').default;
+    return require('../../src/private/webapis/dom/events/CustomEvent').default;
   },
   get createAttributePayload(): createAttributePayload {
     return require('../ReactNative/ReactFabricPublicInstance/ReactNativeAttributePayload')

packages/react-native/Libraries/Events/EventPolyfill.js

@@ -4166,83 +4166,6 @@ declare export default typeof RCTNativeAppEventEmitter;
 "
 `;
 
-exports[`public API should not change unintentionally Libraries/Events/CustomEvent.js 1`] = `
-"type CustomEvent$Options = $ReadOnly<{
-  bubbles?: boolean,
-  cancelable?: boolean,
-  composed?: boolean,
-  detail?: { ... },
-}>;
-declare class CustomEvent extends EventPolyfill {
-  detail: ?{ ... };
-  constructor(typeArg: string, options: CustomEvent$Options): void;
-}
-declare export default typeof CustomEvent;
-"
-`;
-
-exports[`public API should not change unintentionally Libraries/Events/EventPolyfill.js 1`] = `
-"type Event$Init = {
-  bubbles?: boolean,
-  cancelable?: boolean,
-  composed?: boolean,
-  scoped?: boolean,
-  ...
-};
-interface IEvent {
-  constructor(type: string, eventInitDict?: Event$Init): void;
-  +type: string;
-  +target: EventTarget;
-  +srcElement: Element;
-  +currentTarget: EventTarget;
-  composedPath(): Array<EventTarget>;
-  +NONE: number;
-  +AT_TARGET: number;
-  +BUBBLING_PHASE: number;
-  +CAPTURING_PHASE: number;
-  +eventPhase: number;
-  stopPropagation(): void;
-  stopImmediatePropagation(): void;
-  +bubbles: boolean;
-  +cancelable: boolean;
-  preventDefault(): void;
-  +defaultPrevented: boolean;
-  +composed: boolean;
-  +isTrusted: boolean;
-  +timeStamp: number;
-  +deepPath?: () => EventTarget[];
-  +scoped: boolean;
-  initEvent(type: string, bubbles: boolean, cancelable: boolean): void;
-}
-declare class EventPolyfill implements IEvent {
-  type: string;
-  bubbles: boolean;
-  cancelable: boolean;
-  composed: boolean;
-  scoped: boolean;
-  isTrusted: boolean;
-  defaultPrevented: boolean;
-  timeStamp: number;
-  NONE: number;
-  AT_TARGET: number;
-  BUBBLING_PHASE: number;
-  CAPTURING_PHASE: number;
-  eventPhase: number;
-  currentTarget: EventTarget;
-  target: EventTarget;
-  srcElement: Element;
-  constructor(type: string, eventInitDict?: Event$Init): void;
-  composedPath(): Array<EventTarget>;
-  preventDefault(): void;
-  initEvent(type: string, bubbles: boolean, cancelable: boolean): void;
-  stopImmediatePropagation(): void;
-  stopPropagation(): void;
-  setSyntheticEvent(value: mixed): void;
-}
-declare export default typeof EventPolyfill;
-"
-`;
-
 exports[`public API should not change unintentionally Libraries/Image/AssetRegistry.js 1`] = `
 "declare const AssetRegistry: {
   registerAsset: (asset: PackagerAsset) => number,