[iOS] [Android] Fix for Shell custom FlyoutIcon display problem

[Tamilarasan-Paranthaman]

Issue 1: Foreground color of the custom flyout icon is not applied.

Root Cause of the issue

• The tintColor is set to white in the ShellToolBarTracker class, which prevents the foreground color from being applied properly to the tintColor.

Description of Change

• I have resolved the issue by updating the tint color to handle both page and shell foreground color cases, including dynamic scenarios.

Issue 2: The flyout icon is aligned to the center instead of the left, causing the title to extend beyond the view.

Root Cause of the issue

• The custom image size is too large, causing it to render in the center and leaving extra space on the left.

Description of Change

• I resized the custom image to match the hamburger size using the UIGraphics concept and implemented caching to prevent redundant image rendering.

Reference for icon size: https://github.com/dotnet/maui/blob/main/src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellPageRendererTracker.cs#L450

Issues Fixed

Fixes #25920

Tested the behaviour in the following platforms

• [x] Android
• [ ] Windows
• [x] iOS
• [x] Mac

Screenshot

iOS

Before Issue Fix	After Issue Fix

Android"

Before Issue Fix	After Issue Fix

[dotnet-policy-service[bot]]

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]

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