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/Context/State/Code/ApplicationCode.spec.ts

@@ -197,7 +197,7 @@ class UserScriptGeneratorMock implements IUserScriptGenerator {
     selectedScripts: readonly SelectedScript[],
     scriptingDefinition: IScriptingDefinition,
   ): IUserScript {
-    for (const [parameters, result] of Array.from(this.prePlanned)) {
+    for (const [parameters, result] of this.prePlanned) {
       if (selectedScripts === parameters.scripts
         && scriptingDefinition === parameters.definition) {
         return result;