Support for NativeScript v9 sectioned ListView with Angular templates

Is your feature request related to a problem? Please describe.
NativeScript 9 introduced native sectioned ListView support with sticky headers (Announcement). This feature is not yet supported with @nativescript/angular templates.

Describe the solution you'd like
Support for Angular templates in sectioned ListView:

<ListView sectioned="true" stickyHeader="true" [items]="sections">
  <ng-template nsTemplateKey="header" let-section>
    <Label [text]="section.title"></Label>
  </ng-template>
  <ng-template nsTemplateKey="item" let-item>
    <Label [text]="item.name"></Label>
  </ng-template>
</ListView>

Describe alternatives you've considered
Flattening sections into a single array with type discriminator and using itemTemplateSelector, but this loses native sticky header behavior.

Additional context

• @nativescript/core: 9.x
• @nativescript/angular: 20.0.0, 21.0.0-rc0
• iOS / Android

Start at the @nativescript/angular ListView template integration and compare how nsTemplateKey values are handled for item templates. Verify the sectioned and sticky-header example against NativeScript core 9.x on iOS and Android; done means both Angular templates render with native section headers and sticky-header behavior.