Fix allowing using dyanmic import of module instead of async function

[mununki]

This PR fixes not allowing to using the dynamic import of module in the normal function that is not async function.

// should not compiled
let f0 = () => {
  module O = await Belt.Option
  O.forEach
}

// Ok
let f1 = async () => {
  module O = await Belt.Option
  O.forEach
}

Plus, This PR fixes build error using the dynamic import of module in uncurried mode:

// should be fine in uncurried mode
let f1 = async () => {
  module O = await Belt.Option
  O.forEach
}

[mununki]

Ready to get a review

[cristianoc]

Add a test maybe?

[mununki]

Import.res has it already. After this PR is merged, if missing async will break the test.