ObservableCollection<T> range operation support/test plan

### Description

This issue is about the support/testing plan for the new `ObservableCollection` range operations, which were proposed and approved in https://github.com/dotnet/runtime/issues/18087, and that @ahoefling is kindly contributing to the BCL in https://github.com/dotnet/runtime/pull/65101, as well as the necessary fix for WPF. This issue is just for public tracking of the feature, along with its testing plan.

As mentioned in the related issue too, this feature being fully supported is critical for several scenarios, and especially for the MVVM Toolkit, which specifically didn't introduce any kind of polyfills for this, choosing to rely on official support instead.

cc. @BretJohnson, @PureWeen, @jsuarezruiz, @jamesmontemagno

### Public API Changes

No API changes on the MAUI side. This issue is just to track support for range operations in `INotifyCollectionChanged`.

### Intended Use-Case

n/a

> VS bug [#1839535](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1839535)