[Windows] Fix for SearchHandler Fails to Display Results.

[Tamilarasan-Paranthaman]

Root Cause of the issue

• When the SearchHandler's ItemTemplate is null, it applies an incorrect ItemsSource and ItemTemplate to the AutoSuggestBox.

Description of Change

• I resolved the issue by assigning the correct ItemsSource and ItemTemplate from the SearchHandler to the AutoSuggestBox when the SearchHandler's ItemTemplate is null.

Test Case

• The test case has already been added in the following PR. We can reenable it once, it has been merged.
  [Testing] Enabling ported UITests from Xamarin.UITests to Appium - 40 #26491 (ShellSearchHandlerItemSizing)

Reference

https://github.com/dotnet/maui/blob/main/src/Controls/src/Core/Handlers/Items/ItemsViewHandler.Windows.cs#L279

https://github.com/dotnet/maui/blob/main/src/Controls/src/Core/Handlers/Items/ItemsViewHandler.Windows.cs#L267

Issues Fixed

Fixes #26477

Tested the behaviour in the following platforms

• Android
• Windows
• iOS
• Mac

Screenshot

Before Issue Fix	After Issue Fix
SearchHandlerIssueV.mp4	SearchHandlerFix.mp4

[dotnet-policy-service]

Hey there @Tamilarasan-Paranthaman! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.