Refactor SampleCodePresenter to adjust code presenter visibility handling

[Zakariathr22]

Description

Refactored SampleCodePresenter to improve code presenter visibility handling and align its behavior with broader application usage patterns, the only change is:

• Updated the SampleCodePresenter_Loaded method in SampleCodePresenter.xaml.cs to enhance visibility handling for CodePresenter by removing logic to collapse code presenter visibility by default.

Motivation and Context

• The previous implementation collapsed the visibility of CodePresenter in scenarios where it was not explicitly needed. This conflicted with scenarios like the Iconography Page, where an empty CodePresenter is defined and modified dynamically later.
• The responsibility for managing visibility when switching between code presenters (e.g., XAML and C#) already exists in the ControlExample.HandlePresenterVisibility method, making redundant visibility management unnecessary within SampleCodePresenter in most cases.
• To prevent issues in cases requiring default-loaded CodePresenter, its visibility is now set to Visible by default, and changes are applied only when truly needed.

How Has This Been Tested?

Manual Testing:

• Verified CodePresenter visibility remains consistent across pages requiring dynamic updates.
• Tested transitions between XAML and C# in scenarios where HandlePresenterVisibility() manages visibility logic.

Screenshots:

- Before: Code presenters collapsed unnecessarily where they defined empty to be modified dynamically later.

- After: Proper handling of empty code presenters and visibility.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)