[Android] Fixed issue where group Header/Footer template was applied to all items when IsGrouped was true for an ObservableCollection

[Tamilarasan-Paranthaman]

Root Cause of the issue

• The items in the ItemsSource collection were being cast to IEnumerable and added to the groups collection, even when they were not actually of an IEnumerable type. As a result, these individual items were incorrectly treated as groups, leading to group-related behaviors such as the display of group headers and footers.

Description of Change

• I have added a type check to ensure that only items that implement IEnumerable are added to the groups collection. If an item is not an IEnumerable, it will no longer be treated as a group, and the groups collection will remain empty in such cases.

Issues Fixed

Fixes #28827

Tested the behaviour in the following platforms

• iOS
• Android
• Windows
• Mac

Screenshot

Before Fix	After Fix
Before-Fix.mov	After-Fix.mov

[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.

[jsuarezruiz]

/azp run

[azure-pipelines]

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