[iOS] - Fix Custom FlyoutIcon from Being Overridden to Default Color in Shell

[prakashKannanSf3972]

Issue: The color of the custom FlyoutIcon in Shell resets to the default blue instead of retaining its original color.

RootCause

By default, UIImageRenderingMode is set to Automatic, allowing the rendering behavior to be determined based on the UI context. When a custom FlyoutIcon is applied, it does not retain its original color but instead adapts to the predefined tinting behavior, leading to unintended color changes.

Description of Change

The image rendering mode is now set to UIImageRenderingMode.AlwaysOriginal, ensuring that custom icons maintain their original colors without being altered by default rendering behavior.

• When no custom FlyoutIcon is set, its color can still be modified using Shell.ForegroundColor.
• When a custom FlyoutIcon is applied, it now preserves its original image color without automatic tinting.
• If color customization for the custom icon is needed, Shell.ForegroundColor should be set accordingly to allow the color modification to be applied.

Issues Fixed

Fixes #6738

Tested the behaviour in the following platforms

• Android
• Windows
• iOS
• Mac

Output

Before	After

[dotnet-policy-service]

Hey there @prakashKannanSf3972! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.