[core] Improve sleep test helper

The helper was duplicated. I have also added the explict return type
so TypeScript can import the type of the helper faster.

packages/grid/x-data-grid/src/hooks/utils/useGridApiEventHandler.test.tsx

@@ -2,18 +2,13 @@ import * as React from 'react';
 import { spy } from 'sinon';
 import { expect } from 'chai';
 import { createRenderer } from '@mui/monorepo/test/utils';
+import { sleep } from 'test/utils/helperFn';
 import { createUseGridApiEventHandler } from './useGridApiEventHandler';
 import { FinalizationRegistryBasedCleanupTracking } from '../../utils/cleanupTracking/FinalizationRegistryBasedCleanupTracking';
 import { TimerBasedCleanupTracking } from '../../utils/cleanupTracking/TimerBasedCleanupTracking';
 
 const noop = spy();
 
-function sleep(time: number): Promise<void> {
-  return new Promise<void>((res) => {
-    setTimeout(res, time);
-  });
-}
-
 describe('useGridApiEventHandler', () => {
   const { render } = createRenderer();
 

test/utils/helperFn.ts

@@ -3,7 +3,7 @@ import { act } from '@mui/monorepo/test/utils';
 import { unwrapPrivateAPI } from '@mui/x-data-grid/internals';
 import type { GridApiCommon } from '@mui/x-data-grid/models/api/gridApiCommon';
 
-export function sleep(duration: number) {
+export function sleep(duration: number): Promise<void> {
   return new Promise<void>((resolve) => {
     setTimeout(() => {
       resolve();