[Testing] Added tests to validate the ItemsUpdatingScrollMode property in CarouselView

[jsuarezruiz]

Description of Change

Added tests to validate the ItemsUpdatingScrollMode property in CarouselView.

Issues Fixed

Related with #25991

[rmarinho]

/rebase

[rmarinho]

Test is failing in several platforms

[jsuarezruiz]

/rebase

[jsuarezruiz]

The default value for the ItemsUpdatingScrollMode property is KeepItemsInView

maui/src/Controls/src/Core/Items/ItemsUpdatingScrollMode.cs

Line 7 in 44743ae

/// <include file="../../../docs/Microsoft.Maui.Controls/ItemsUpdatingScrollMode.xml" path="Type[@FullName='Microsoft.Maui.Controls.ItemsUpdatingScrollMode']/Docs/*" />

So, by default, the CarouselView should move the scroll to the first item after add a new one. That happens on Windows, after merge c3f42a9

In the added UITest we can validate the behavior with the three enum options:

• KeepItemsInView keeps the first item in the list displayed when new items are added.
• KeepScrollOffset ensures that the current scroll position is maintained when new items are added.
• KeepLastItemInView adjusts the scroll offset to keep the last item in the list displayed when new items are added.

However, as described in the issue, on Android the position is maintained by default. That's wrong. However, more than fix the Windows behavior, seems like it is wrong on other platforms. @Tamilarasan-Paranthaman Could you check the tests results and align/fix the behavior between platforms?

Close in favor of #26608