Migrate Android Shell over to using all the same platform structures as non-shell

[PureWeen]

• Takes us a step closer towards Make Shell compatible with the other page types in .NET MAUI #6389. WinUI already uses shared code between Shell and Non Shell.
• Massively reduces maintenance burden by obsoleting all existing android specific shell code.
• Performance. The newer structures we are using for FlyoutPage/NavigationPage perform slightly better than the current shell platform code. Plus this reduces the amount of code we have to tune through AOT profiles and keep track of as it relates to ensuring code paths stay performant.

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.