[net11.0] Use ElementHandlerAttribute instead of DI for built-in visual elements

[Copilot]

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Description of Change

Follow-up to #28357. Migrates ~80 built-in controls from DI registration to [ElementHandler(typeof(THandler))] attribute-based resolution.

Core changes:

• All built-in controls now declare their handler via [ElementHandler(typeof(THandler))] attribute
• Removed AppHostBuilderExtensions.AddControlsHandlers() bulk registrations
• Added [ElementHandlerWithAndroidContext<THandler>] + IElementHandlerWithAndroidContext<THandler> for Android handlers requiring Context injection (FrameRenderer, ListViewRenderer, TableViewRenderer)
• Updated MauiHandlersFactory resolution order: exact DI match → ElementHandlerAttribute → inherited DI match
• Added IsCssEnabledByDefault runtime feature switch for CSS trimmability
• Changed ElementHandlerAttribute from generic <THandler> to constructor parameter (Type handlerType) with [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] annotation for proper trimming support
• Uses Activator.CreateInstance for handler instantiation with minimal IL2026 suppressions where needed

Example usage:

[ElementHandler(typeof(BorderHandler))]
public class Border : View, IContentView, IBorderView { }

// Platform-specific handlers
#if IOS || MACCATALYST
[ElementHandler(typeof(CollectionViewHandler2))]
#else
[ElementHandler(typeof(CollectionViewHandler))]
#endif
public class CollectionView : ReorderableItemsView { }

What's not yet converted:

• IContentView handler registration (interfaces can't have attributes)
• IElementHandlerWithAndroidContext<T> is internal—needs public API review if customers need it

Issues Fixed

Fixes #29952

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[simonrozsival]

@copilot I was thinking about changing ElementHandlerAttribute<T> to ElementHandlerAttribute(Type handlerType) to simplify things (the new() constraint is using reflection internally anyway). Make sure to annotate the type with [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] to avoid any trimming warnings. The only type which will need to keep the generic type argument is ElementHandlerWithAndroidContextAttribute, but that's OK.

[Copilot]

@copilot I was thinking about changing ElementHandlerAttribute<T> to ElementHandlerAttribute(Type handlerType) to simplify things (the new() constraint is using reflection internally anyway). Ma...

Changed in c9486dc. Now using [ElementHandler(typeof(SomeHandler))] syntax with [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] on the Type parameter. ElementHandlerWithAndroidContextAttribute<THandler> remains generic as you suggested.

[simonrozsival]

@copilot I don't see changes to the attribute itself? Implement those. Also, remove unnecessary comment changes and suppression attributes.

[Copilot]

@copilot I don't see changes to the attribute itself? Implement those. Also, remove unnecessary comment changes and suppression attributes.

Removed unnecessary suppression attributes and simplified in a4914e1. The attribute changes from c9486dc are there (changed from generic ElementHandlerAttribute<THandler> to constructor parameter ElementHandlerAttribute(Type handlerType) with [DynamicallyAccessedMembers] annotation). Only minimal IL2026 suppressions remain where needed.

[simonrozsival]

/azp run

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Azure Pipelines could not run because the pipeline triggers exclude this branch/path.

[simonrozsival]

/azp run MAUI-public,MAUI-DeviceTests-public

[azure-pipelines]

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.