Leakage in async computation awaiting for a ValueTask

this code

```
let rec streamLoop (enumerator: IAsyncEnumerator<'reply>) = async {
let! hasNext = enumerator.MoveNextAsync()

if hasNext then
try onNewItem enumerator.Current with | _ -> ()
return! streamLoop enumerator }
```

creates a memory leak. Memory in Visual Studio Diagnostic Tools reveal a constantly increasing number of `ContinuationTaskFromResultTask`.

Fix simply adding .AsTask() |> Async.AwaitTask

```
let rec streamLoop (enumerator: IAsyncEnumerator<'reply>) = async {
let! hasNext = enumerator.MoveNextAsync().AsTask() |> Async.AwaitTask

if hasNext then
try onNewItem enumerator.Current with | _ -> ()
return! streamLoop enumerator }
```
Suggests incorrrect interaction of F# Async with ValueTask<> or IAsyncEnumerator<>.MoveNextAsync()