Responsive FlyoutBehavior

### Description

Currently there are 3 options available for the FlyoutBehavior setting: `Disabled`, `Flyout` and `Locked`
It'd be nice to have a responsive setting which reacts to the width of the screen, Similar to how the Windows 10 & 11 settings menu has been implemented.

Example:

https://user-images.githubusercontent.com/4095127/168296567-c8edc9ec-de8c-42e7-86c1-2290072499b0.mp4

In the past the Xamarin.Forms FlyoutPage featured the following options: `Default`, `Popover`, `Split`, `SplitOnLandscape`, `SplitOnPortrait`.
https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/navigation/flyoutpage#control-the-detail-page-layout-behavior

However,
> **Important**
> The value of the [FlyoutLayoutBehavior](https://docs.microsoft.com/en-us/dotnet/api/xamarin.forms.flyoutpage.flyoutlayoutbehavior#xamarin-forms-flyoutpage-flyoutlayoutbehavior) property only affects applications running on tablets or the desktop. Applications running on phones always have the Popover behavior.

Additionally I don't believe the FlyoutLayoutBehavior was able to react to window sized changed events.

### Public API Changes

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### Intended Use-Case

This feature would be useful in Windows & macOS applications as the content area can be resized.
Additionally this feature is common on tablet formfactors, specifically when transitioning from landscape to portrait orientation.

The issue proposes a new Responsive value for Shell.FlyoutBehavior, adapting the flyout to window width on Windows, macOS, and tablets. Start by locating the FlyoutBehavior implementation and existing tests; done means the behavior responds to resizing and orientation changes across the stated form factors, with the proposed XAML API working.

Written by the indexing model from the issue text.