Popups: [Proposal] Add Overlay Color Change Property

[ElegantCatterpillar]

A Popup property to be able to change the color of the overlay, currently it is a transparent Medium color.

In some cases I have needed to make the color transparent, or to make the color stronger or weaker. More so when I created custom components from the Popup.

For example use:
OverlayColor = "Transparent"

<toolkit:Popup
xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
CanBeDismissedByTappingOutsideOfPopup="True"
OverlayColor="Green"
Color="Red">
</toolkit:Popup>

[CliffAgius]

Closing as Duplicate of #1799