Nested `startTransition` call "takes over" and makes parent `startTransition` unable to track `isPending`.

Seb says it's a bug.

Repro:

https://codesandbox.io/s/pensive-breeze-rg70wn?file=/IndexPage.js:192-288

1. Click the button
2. `isPending` in `IndexPage.js` is `true`

However, `isPending` in `App.js` is `false`.

Expected: `isPending` in `App.js` is also `true`.
}
      }
    }
    
    
    
    
    
    
    
    const root: FiberRoot | null = getWorkInProgressRoot();
    if (root === null) {
      throw new Error(
        'Expected a work-in-progress root. This is a bug in React. Please file an issue.',
      );
    }
    if (!includesBlockingLane(root, renderLanes)) {
      pushStoreConsistencyCheck(fiber, getSnapshot, nextSnapshot);
    }
  }
  
  
  
  hook.memoizedState = nextSnapshot;
  const inst: StoreInstance<T> = {
    value: nextSnapshot,
    getSnapshot,
  };
  hook.queue = inst;
   Schedule an effect to subscribe to the store.