Refactor to improve iterations

- Use function abstractions (such as map, reduce, filter etc.) over
  for-of loops to gain benefits of having less side effects and easier
  readability.
- Enable `downLevelIterations` for writing modern code with lazy evaluation.
- Refactor for of loops to named abstractions to clearly express their
  intentions without needing to analyse the loop itself.
- Add missing cases for changes that had no tests.

src/infrastructure/Events/EventSource.ts

@@ -12,7 +12,7 @@ export class EventSource<T> implements IEventSource<T> {
   }
 
   public notify(data: T) {
-    for (const handler of Array.from(this.handlers.values())) {
+    for (const handler of this.handlers.values()) {
       handler(data);
     }
   }