message: refactor(core): remove Renderer3-related cleanup code paths
  Renderer3 had to store reference to the listener function in order to
  properly cleanup event listeners. Since the Renderer3 abstraction was
  removed the corresponding code path is no longer needed (Renderer2
  returns a cleanup function that can be called directly).
  PR Close
diff: import {ViewEncapsulation} from '../metadata/view';
  import {RendererStyleFlags2} from '../render/api_flags';
  import {addToArray, removeFromArray} from '../util/array_utils';
  -import {assertDefined, assertEqual, assertFunction, assertString} from '../util/assert';
  +import {assertDefined, assertEqual, assertFunction, assertNumber, assertString} from '../util/assert';
  import {escapeCommentText} from '../util/dom';
  import {assertLContainer, assertLView, assertParentView, assertProjectionSlots, assertTNodeForLView} from './assert';
  @@ -451,24 +451,16 @@ function processCleanups(tView: TView, lView: LView): void {
  if (tCleanup !== null) {
  for (let i = 0; i < tCleanup.length - 1; i += 2) {
  if (typeof tCleanup[i] === 'string') {
  - // This is a native DOM listener
  - const idxOrTargetGetter = tCleanup[i + 1];
  - const target = typeof idxOrTargetGetter === 'function' ?
  - idxOrTargetGetter(lView) :
  - unwrapRNode(lView[idxOrTargetGetter]);
  - const listener = lCleanup[lastLCleanupIndex = tCleanup[i + 2]];
  - const useCaptureOrSubIdx = tCleanup[i + 3];
  - if (typeof useCaptureOrSubIdx === 'boolean') {
  - // native DOM listener registered with Renderer3
  - target.removeEventListener(tCleanup[i], listener, useCaptureOrSubIdx);
  - } else {
  - if (useCaptureOrSubIdx >= 0) {
  + // This is a native DOM listener. It will occupy 4 entries in the TCleanup array (hence i +=
  + // 2 at the end of this block).
  + const targetIdx = tCleanup[i + 3];
  + ngDevMode && assertNumber(targetIdx, 'cleanup target must be a number');
  + if (targetIdx >= 0) {
  // unregister
  - lCleanup[lastLCleanupIndex = useCaptureOrSubIdx]();
  + lCleanup[lastLCleanupIndex = targetIdx]();
  } else {
  // Subscription
  - lCleanup[lastLCleanupIndex = -useCaptureOrSubIdx].unsubscribe();
  - }
  + lCleanup[lastLCleanupIndex = -targetIdx].unsubscribe();
  }
  i += 2;
  } else {
  