Unhook Page from embedded Application on disposal

[hartez]

Description of Change

Unhook Page from embedded Application on disposal so the Page can be collected.

This is a supplementary fix to #6636; that change allowed Pages which were not hooked to the current Application object to be collected, but did not allow the most recent Page associated with the Application to be collected. This change allows the most recent page to be collected.

Issues Resolved

• additional fix for Xamarin Forms Native embedding Memory issue #4671

API Changes

Application.cs

Added:
protected internal virtual void CleanUp();

Modified:
public NavigationProxy NavigationProxy { get; } => public NavigationProxy NavigationProxy { get; private set; }

Platforms Affected

• Core/XAML (all platforms)
• iOS

Behavioral/Visual Changes

None

Before/After Screenshots

Not applicable

PR Checklist

• Has automated tests
• Rebased on top of the target branch at time of PR
• Changes adhere to coding standard