Specifically `An update to * inside a test was not wrapped in act(...)` is not logged when a prior update threw. 

<details>
<summary>failing test (#21766)</summary>

```js
// @gate __DEV__
it('warns if a setState is called outside of act(...) after a component threw', () => {
  let setValue = null;
  function App({defaultValue}) {
    if (defaultValue === undefined) {
      throw new Error();
    }
    const [value, _setValue] = React.useState(defaultValue);
    setValue = _setValue;
    return value;
  }

  expect(() => {
    act(() => {
      render(<App defaultValue={undefined} />, container);
    });
  }).toThrow();

  act(() => {
    rerender(<App defaultValue={0} />, container);
  });

  expect(() => setValue(1)).toErrorDev([
    'An update to App inside a test was not wrapped in act(...).',
  ]);
});
```
</details>

What I noticed is that in https://github.com/facebook/react/blob/27c9c95e23ddedb9163373950e364dd62038f6c0/packages/react-reconciler/src/ReactFiberWorkLoop.new.js#L2855-L2865
the `executionContext` will still equal `RetryAfterError` when we would expect a "missing act" warning.

"missing act" warnings are working as expected with legacy roots.
const previousPriority = getCurrentUpdatePriority();
  try {
    ReactCurrentBatchConfig.transition = 0;
    setCurrentUpdatePriority(DiscreteEventPriority);
    if (fn) {
      return fn(a);
    } else {
      return (undefined: $FlowFixMe);
    }
  } finally {
    setCurrentUpdatePriority(previousPriority);
    ReactCurrentBatchConfig.transition = prevTransition;
    executionContext = prevExecutionContext;
     
     
     
    if ((executionContext & (RenderContext | CommitContext)) === NoContext) {
      flushSyncCallbacks();
    }
  }
}
export function flushSync<A, R>(fn: A => R, a: A): R {
  if (__DEV__) {
    if ((executionContext & (RenderContext | CommitContext)) !== NoContext) {
      console.error(
        'flushSync was called from inside a lifecycle method. React cannot ' +
          'flush when React is already rendering. Consider moving this call to ' +
          'a scheduler task or micro task.',
      );
    }