feat(animations): support styling of the default animation state

It is now possible to set a fallback state that will apply its
styling when the destination state is not detected.

```ts
state("*", style({ ... }))
```

Closes #9013

modules/playground/src/animate/app/animate-app.ts

@@ -17,7 +17,9 @@ import {
     <div @backgroundAnimation="bgStatus">
       <button (click)="state='start'">Start State</button>
       <button (click)="state='active'">Active State</button>
+      |
       <button (click)="state='void'">Void State</button>
+      <button (click)="state='default'">Unhandled (default) State</button>
       <button style="float:right" (click)="bgStatus='blur'">Blur Page</button>
       <hr />
       <div *ngFor="let item of items" class="box" @boxAnimation="state">
@@ -34,6 +36,7 @@ import {
       ])
     ]),
     trigger("boxAnimation", [
+      state("*", style({ "height": "*", "background-color": "#dddddd", "color":"black" })),
       state("void, hidden", style({ "height": 0, "opacity": 0 })),
       state("start", style({ "background-color": "red", "height": "*" })),
       state("active", style({ "background-color": "orange", "color": "white", "font-size":"100px" })),
@@ -65,15 +68,15 @@ export class AnimateApp {
   get state() { return this._state; }
   set state(s) {
     this._state = s;
-    if (s == 'start' || s == 'active') {
+    if (s == 'void') {
+      this.items = [];
+    } else {
       this.items = [
         1,2,3,4,5,
         6,7,8,9,10,
         11,12,13,14,15,
         16,17,18,19,20
       ];
-    } else {
-      this.items = [];
     }
   }
 }