unify usage of sleepAsync and add tests

The tests mock JS setTimeout API. However promise.resolve() is not working without flushing the promise queue (which could be done just by awaiting Promise.resolve()), similar issue has been discussed in facebook/jest#2157.

src/infrastructure/Threading/AsyncSleep.ts

@@ -0,0 +1,5 @@
+export type SchedulerType = (callback: (...args: any[]) => void, ms: number) => void;
+
+export function sleepAsync(time: number, scheduler: SchedulerType = setTimeout) {
+    return new Promise((resolve) => scheduler(() => resolve(undefined), time));
+}