docs(material/autocomplete): reset template driven autocomplete example (#27656)

Make a bug fix to the template-driven autocomplete example. Fix demo
issue where clicking the reset button doesn't reset the autocomplete
options and the value in the input to the original state. Reset the form
field by resetting the value of the input and the tdStates to the value
when the demo is first rendered.

(cherry picked from commit 5fca612)

Author: zarend

src/dev-app/autocomplete/autocomplete-demo.html

@@ -83,7 +83,7 @@
     </mat-form-field>
 
     <p>
-      <button mat-button (click)="modelDir.reset()">RESET</button>
+      <button mat-button (click)="clearTemplateState()">RESET</button>
       <button mat-button (click)="currentState='California'">SET VALUE</button>
       <button mat-button (click)="tdDisabled=!tdDisabled">
         TOGGLE DISABLED

src/dev-app/autocomplete/autocomplete-demo.ts

@@ -187,6 +187,12 @@ export class AutocompleteDemo {
     return this._isStateDisabled(index, this.templateDisableStateOption);
   }
 
+  clearTemplateState() {
+    this.modelDir.reset();
+    this.currentState = '';
+    this.tdStates = this.states.slice();
+  }
+
   private _isStateDisabled(stateIndex: number, disableStateOption: DisableStateOption) {
     if (disableStateOption === 'all') {
       return true;