arc.http[.async] in version 7.0.0 are overly strict regarding mixing sync and async middleware

[alexbepple]

Is your feature request related to a problem? Please describe.

If my handler looks like the following, the arc.http and arc.http.async helpers in version 7.0.0 will complain with

TypeError: All arc.http middleware functions must be async

console logEvent = (event) => {
  console.log(event)
  return event
}

export const handler = arc.http(
  logEvent,

  async () => {
    // do async work
  },
)

However, it would be quite weird to have to turn the above logEvent into an async function.

Describe the solution you'd like
If you want to keep supporting the callback interface, I think it would be best to stick with the API of versions <7. Version 7.0.0 forces me to make functions async that are not async in nature.

Describe alternatives you've considered
An alternative could be to have arc.http be 'smart' the way it currently is in 7.0.0, but arc.http.async to behave the way it did <7.