Errors are not thrown inside async functions while streaming

[QuiiBz]

When errors are thrown after the return new Response(...) while streaming, the runtime hangs and never timeout or error. Instead, errors should be propagated and the timeout should stop the execution if it's hanging indefinitely.

Reproduction code:

export async function handler() {
  const { readable } = new TransformStream();

  async function hang() {
    doesNotExists();
  }

  hang();

  return new Response(readable);
}