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.

tests/unit/application/Common/ScriptingLanguage/ScriptingLanguageFactoryTestRunner.ts

@@ -25,7 +25,7 @@ function testExpectedInstanceTypes<T>(
 ) {
   describe('create returns expected instances', () => {
     // arrange
-    for (const language of Array.from(expectedTypes.keys())) {
+    for (const language of expectedTypes.keys()) {
       it(ScriptingLanguage[language], () => {
         // act
         const expected = expectedTypes.get(language);