React version: v17.0.1

## Steps To Reproduce

1. `npx create-react-app myapp`
2. `cd myapp && npm start`
3. Open http://localhost:3000 in **Chrome 88 or 89, regular or Incognito mode**
4. Open DevTools: the warning is displayed

Link to code example: https://react-z95km1.stackblitz.io/
https://stackblitz.com/edit/react-z95km1

## The current behavior

Warning: `scheduler.development.js:298 [Deprecation] SharedArrayBuffer will require cross-origin isolation as of M91, around May 2021. See https://developer.chrome.com/blog/enabling-shared-array-buffer/ for more details.`

## The expected behavior

No warning will be shown.

As the warning shows, Chrome will require cross-origin isolation starting version 91 in order to use SharedArrayBuffer. To enable cross-origin isolation, the page needs to be loaded with COOP and COEP headers which I believe is out of React's control. You can learn more about this at https://developer.chrome.com/blog/enabling-shared-array-buffer/.

As it's confusing for React users to see this warning every time they open the page, I'd propose two things:

1. Suppress the message by using SAB only when cross-origin isolation is enabled. You can check it by `self.crossOriginIsolated` boolean flag.
2. Document that the page needs to send COOP and COEP headers to profile performance using SharedArrayBuffer. You can find an actionable guide here: https://web.dev/cross-origin-isolation-guide/

The problematic code is here: https://github.com/facebook/react/blob/master/packages/scheduler/src/SchedulerProfiling.js#L21-L22

FWIW, with cross-origin isolation, you'll be able to use [JS Self-Profiling API](https://wicg.github.io/js-self-profiling/) too.

cc: @acomminos @maudnals
if (eventLog !== null) {
      
      
      
      logEvent([TaskStartEvent, ms * 1000, task.id, task.priorityLevel]);
    }
  }
}
export function markTaskCompleted(
  task: {
    id: number,
    priorityLevel: PriorityLevel,
    ...
  },
  ms: number,
) {
  if (enableProfiling) {
    profilingState[PRIORITY] = NoPriority;
    profilingState[CURRENT_TASK_ID] = 0;
    profilingState[QUEUE_SIZE]--;