fix(animations): only use the WA-polyfill alongside AnimationBuilder (#22143)

This patch removes the need to include the Web Animations API Polyfill
(web-animations-js) as a dependency. Angular will now fallback to using
CSS Keyframes in the event that `element.animate` is no longer supported
by the browser.

In the event that an application does use `AnimationBuilder` then the
web-animations-js polyfill is required to enable programmatic,
position-based access to an animation.

Closes #17496

PR Close #22143

tools/public_api_guard/animations/browser.d.ts

@@ -2,7 +2,7 @@
 export declare abstract class AnimationDriver {
     abstract animate(element: any, keyframes: {
         [key: string]: string | number;
-    }[], duration: number, delay: number, easing?: string | null, previousPlayers?: any[]): any;
+    }[], duration: number, delay: number, easing?: string | null, previousPlayers?: any[], scrubberAccessRequested?: boolean): any;
     abstract computeStyle(element: any, prop: string, defaultValue?: string): string;
     abstract containsElement(elm1: any, elm2: any): boolean;
     abstract matchesElement(element: any, selector: string): boolean;