Xmlns perf

[StephaneDelcroix]

Note

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It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Description of Change

Issues Fixed

Fixes #

[Copilot]

Pull Request Overview

This PR modernizes various parts of the Controls codebase by updating nullability annotations, improving method signatures, and addressing obsolete API usage while introducing performance‐related improvements for XML namespace processing. Key changes include:

• Updating type converter and binding method signatures to use nullable context (e.g. in ImageSourceConverter, GridLengthTypeConverter, FontSizeConverter).
• Converting several public API properties (such as those in DatePicker) from non‑nullable types to nullable, and adjusting internal remapping and event handling methods.
• Adding pragma directives to suppress obsolete API warnings in platform‑specific handlers.

Reviewed Changes

Copilot reviewed 291 out of 977 changed files in this pull request and generated no comments.

File	Description
src/Controls/src/Core/DatePicker/DatePicker.cs	Changed Date, MinimumDate, and MaximumDate BindableProperties and public properties to use nullable DateTime.
src/Controls/src/Core/Element/Element.Mapper.cs	Introduced a static constructor that calls RemapIfNeeded to update element mappings.
src/Controls/src/Core/IExtendedTypeConverter.cs	Updated the ConvertFromInvariantString signature to return nullables.
src/Controls/src/Core/FontImageSource.cs	Added a ContentProperty attribute for the Glyph property.

Comments suppressed due to low confidence (1)

src/Controls/src/Core/DatePicker/DatePicker.cs:20

• Changing the Date, MinimumDate, and MaximumDate properties from non-nullable DateTime to nullable DateTime? in DatePicker constitutes a breaking change in the public API. Please confirm that all consumers of these properties are updated to handle null values appropriately.

			defaultValueCreator: (bindable) => DateTime.Today);

[PureWeen]

Failing tests are unrelated