fix(angular): remove the tabindex set by routerLink from Ionic components (#29744)

Issue number: resolves #20632

---------

## What is the current behavior?
When using the `routerLink` directive in Angular, it automatically adds
`tabindex="0"` to the element. This creates issues with Ionic components
that render native button or anchor elements, as they have their own
focus management. As a result, when navigating between list items with
`routerLink` using the `Tab` key, you need to press the `Tab` key twice
to move to the next item. This problem is illustrated in the following
demo:

[![Open in
StackBlitz](https://developer.stackblitz.com/img/open_in_stackblitz.svg)](https://stackblitz.com/edit/angular-blfa7h?file=src%2Fapp%2Fexample.component.html)

Related Angular issue: https://github.com/angular/angular/issues/28345

## What is the new behavior?
Updated our `RouterLinkDelegateDirective` to check if the element using
`routerLink` is one of the following Ionic components:
`ion-back-button`, `ion-breadcrumb`, `ion-button`, `ion-card`,
`ion-fab-button`, `ion-item`, `ion-item-option`, `ion-menu-button`,
`ion-segment-button`, or `ion-tab-button`. If so, it removes the
`tabindex` attribute from the element. This allows these Ionic
components to let the native button or anchor element handle the focus.

This solution is demonstrated in the following demo:

[![Open in
StackBlitz](https://developer.stackblitz.com/img/open_in_stackblitz.svg)](https://stackblitz.com/edit/angular-blfa7h-svmguh?file=src%2Fapp%2Fexample.component.html)

> [!NOTE]
> I did not include the `ion-router-link` component in the list to
remove `tabindex` because [the router link
documentation](https://ionicframework.com/docs/api/router-link) does not
recommend using it with Angular:
>> Note: this component should only be used with vanilla and Stencil
JavaScript projects. For Angular projects, use an `<a>` and `routerLink`
with the Angular router.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

## Other information

Dev build: `8.2.7-dev.11722448707.1e8c66e6`

packages/angular/common/src/directives/navigation/router-link-delegate.ts

@@ -31,12 +31,45 @@ export class RouterLinkDelegateDirective implements OnInit, OnChanges {
 
   ngOnInit(): void {
     this.updateTargetUrlAndHref();
+    this.updateTabindex();
   }
 
   ngOnChanges(): void {
     this.updateTargetUrlAndHref();
   }
 
+  /**
+   * The `tabindex` is set to `0` by default on the host element when
+   * the `routerLink` directive is used. This causes issues with Ionic
+   * components that wrap an `a` or `button` element, such as `ion-item`.
+   * See issue https://github.com/angular/angular/issues/28345
+   *
+   * This method removes the `tabindex` attribute from the host element
+   * to allow the Ionic component to manage the focus state correctly.
+   */
+  private updateTabindex() {
+    // Ionic components that render a native anchor or button element
+    const ionicComponents = [
+      'ION-BACK-BUTTON',
+      'ION-BREADCRUMB',
+      'ION-BUTTON',
+      'ION-CARD',
+      'ION-FAB-BUTTON',
+      'ION-ITEM',
+      'ION-ITEM-OPTION',
+      'ION-MENU-BUTTON',
+      'ION-SEGMENT-BUTTON',
+      'ION-TAB-BUTTON',
+    ];
+    const hostElement = this.elementRef.nativeElement;
+
+    if (ionicComponents.includes(hostElement.tagName)) {
+      if (hostElement.getAttribute('tabindex') === '0') {
+        hostElement.removeAttribute('tabindex');
+      }
+    }
+  }
+
   private updateTargetUrlAndHref() {
     if (this.routerLink?.urlTree) {
       const href = this.locationStrategy.prepareExternalUrl(this.router.serializeUrl(this.routerLink.urlTree));