refactor(platform): change deprecated APIs for version 10 (#19347)

Changes the APIs that were deprecated for v10 in the `cdk/platform` module.

BREAKING CHANGES:
* The `_platformId` parameter in the `Platform` constructor is now required.

Author: crisbeto

src/cdk/a11y/focus-trap/focus-trap.spec.ts

@@ -1,5 +1,5 @@
 import {Platform} from '@angular/cdk/platform';
-import {Component, PLATFORM_ID, ViewChild} from '@angular/core';
+import {Component, ViewChild} from '@angular/core';
 import {async, ComponentFixture, TestBed} from '@angular/core/testing';
 import {A11yModule, FocusTrap, CdkTrapFocus} from '../index';
 
@@ -48,9 +48,9 @@ describe('FocusTrap', () => {
       // focus event handler directly.
       const result = focusTrapInstance.focusLastTabbableElement();
 
-      const platformId = TestBed.inject(PLATFORM_ID);
+      const platform = TestBed.inject(Platform);
       // In iOS button elements are never tabbable, so the last element will be the input.
-      const lastElement = new Platform(platformId).IOS ? 'input' : 'button';
+      const lastElement = platform.IOS ? 'input' : 'button';
 
       expect(document.activeElement!.nodeName.toLowerCase())
           .toBe(lastElement, `Expected ${lastElement} element to be focused`);

src/cdk/a11y/high-contrast-mode/high-contrast-mode-detector.spec.ts

@@ -5,14 +5,15 @@ import {
   HighContrastModeDetector, WHITE_ON_BLACK_CSS_CLASS,
 } from './high-contrast-mode-detector';
 import {Platform} from '@angular/cdk/platform';
+import {inject} from '@angular/core/testing';
 
 
 describe('HighContrastModeDetector', () => {
   let fakePlatform: Platform;
 
-  beforeEach(() => {
-    fakePlatform = new Platform();
-  });
+  beforeEach(inject([Platform], (p: Platform) => {
+    fakePlatform = p;
+  }));
 
   it('should detect NONE for non-browser platforms', () => {
     fakePlatform.isBrowser = false;