Don't close Flyout on move

[chucker]

Is your feature request related to a problem? Please describe

In WinUI 3 Gallery, if you open the flyout (tap 'Empty cart'), you can move the gallery window around and have the flyout with it. The flyout does close if you click somewhere, but not if you click and hold on the title bar.

In WPF UI Gallery, that is not so, as of c8cd75f. Instead, trying to move the window closes the flyout.

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Describe alternatives you've considered

No response

Additional context

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