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/stubs/ExpressionsCompilerStub.ts

@@ -58,12 +58,9 @@ function deepEqual(
   if (!scrambledEqual(expectedParameterNames, actualParameterNames)) {
     return false;
   }
-  for (const parameterName of expectedParameterNames) {
+  return expectedParameterNames.every((parameterName) => {
     const expectedValue = expected.getArgument(parameterName).argumentValue;
     const actualValue = actual.getArgument(parameterName).argumentValue;
-    if (expectedValue !== actualValue) {
-      return false;
-    }
-  }
-  return true;
+    return expectedValue === actualValue;
+  });
 }