Remove JSEventLoopWatchdog from react-native package (#51614)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51614

`JSEventLoopWatchdog` is not used in react-native package. This diff moves it to rn-tester which previously deep imported it from react-native (which we want to avoid).

Changelog:
[Internal]

Reviewed By: huntie

Differential Revision: D75410548

fbshipit-source-id: d4996742578e3b068e7acad9479394388b1907ac

packages/react-native/Libraries/__tests__/__snapshots__/public-api-test.js.snap

@@ -4722,22 +4722,6 @@ declare export default typeof InteractionManagerStub;
 "
 `;
 
-exports[`public API should not change unintentionally Libraries/Interaction/JSEventLoopWatchdog.js 1`] = `
-"type Handler = {
-  onIterate?: () => void,
-  onStall: (params: { lastInterval: number, busyTime: number, ... }) => ?string,
-  ...
-};
-declare const JSEventLoopWatchdog: {
-  getStats: () => Object,
-  reset: () => void,
-  addHandler: (handler: Handler) => void,
-  install: ($$PARAM_0$$: { thresholdMS: number, ... }) => void,
-};
-declare export default typeof JSEventLoopWatchdog;
-"
-`;
-
 exports[`public API should not change unintentionally Libraries/Interaction/NativeFrameRateLogger.js 1`] = `
 "export * from \\"../../src/private/specs_DEPRECATED/modules/NativeFrameRateLogger\\";
 declare export default typeof NativeFrameRateLogger;

packages/rn-tester/js/utils/useJsStalls.js

@@ -56,8 +56,7 @@ const useJsStalls = (): ({
   }, []);
 
   const onEnableJsStallsTracking = useCallback(() => {
-    const JSEventLoopWatchdog =
-      require('react-native/Libraries/Interaction/JSEventLoopWatchdog').default;
+    const JSEventLoopWatchdog = require('./JSEventLoopWatchdog').default;
 
     JSEventLoopWatchdog.install({thresholdMS: 25});