build(bazel): Turning on strictPropertyInitialization for Angular. (#24572)

All errors for existing fields have been detected and suppressed with a
`!` assertion.

Issue/24571 is tracking proper clean up of those instances.

One-line change required in ivy/compilation.ts, because it appears that
the new syntax causes tsickle emitted node to no longer track their
original sourceFiles.

PR Close #24572

packages/animations/browser/src/dsl/animation_timeline_builder.ts

@@ -586,7 +586,8 @@ export class AnimationTimelineContext {
 
 export class TimelineBuilder {
   public duration: number = 0;
-  public easing: string|null;
+  // TODO(issue/24571): remove '!'.
+  public easing !: string | null;
   private _previousKeyframe: ɵStyleData = {};
   private _currentKeyframe: ɵStyleData = {};
   private _keyframes = new Map<number, ɵStyleData>();