fix(material/select): open handler invoked twice

Fixes that the select's `open` handler was being called twice: once from the trigger's `click` handler and once from the `onContainerClick` callback when the event propagates.

Fixes #33116.

Author: crisbeto

goldens/material/select/index.api.md

@@ -361,6 +361,8 @@ export class MatSelect implements AfterContentInit, OnChanges, OnDestroy, OnInit
     tabIndex: number;
     toggle(): void;
     trigger: ElementRef;
+    // (undocumented)
+    protected _triggerClicked(event: Event): void;
     get triggerValue(): string;
     typeaheadDebounceInterval: number;
     updateErrorState(): void;

src/material/select/select.html

@@ -1,7 +1,7 @@
 <div
   cdk-overlay-origin
   class="mat-mdc-select-trigger"
-  (click)="open()"
+  (click)="_triggerClicked($event)"
   #fallbackOverlayOrigin="cdkOverlayOrigin"
   #trigger
 >

src/material/select/select.ts

@@ -1018,6 +1018,12 @@ export class MatSelect
     return !this._selectionModel || this._selectionModel.isEmpty();
   }
 
+  protected _triggerClicked(event: Event) {
+    // Stop propagation so it doesn't reach `onContainerClicked`.
+    event.stopPropagation();
+    this.open();
+  }
+
   private _initializeSelection(): void {
     // Defer setting the value in order to avoid the "Expression
     // has changed after it was checked" errors from Angular.