Implement "AdaptiveColumnsPanel"

[giovanni-a]

A responsive that dynamically switches between layouts based on its width:

• when its width meets or exceeds NoColumnsBelowWidth, children are arranged into equal-width columns (one per visible child);
• otherwise, they are stacked vertically in a single column.

Child horizontal and vertical alignments are respected within each allocated slot.

Example of usage:

<Page
    x:Class="FastControls.TestApp.Pages.TestAdaptiveColumnsPanel"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:controlskit="clr-namespace:OpenSilver.ControlsKit;assembly=OpenSilver.ControlsKit.Controls" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" d:DesignWidth="512" d:DesignHeight="932" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d">
    <controlskit:AdaptiveColumnsPanel NoColumnsBelowWidth="400" VerticalAlignment="Top">
        <Border Height="100" CornerRadius="20" Margin="5" Background="#CC505E00">
            <TextBlock Text="Content 1" HorizontalAlignment="Center" Foreground="White" Margin="0,10,0,0"/>
        </Border>
        <Border Height="100" CornerRadius="20" Margin="5" Background="#CC7D0030">
            <TextBlock Text="Content 2" HorizontalAlignment="Center" Foreground="White" Margin="0,10,0,0"/>
        </Border>
        <Border Height="100" CornerRadius="20" Margin="5" Background="#CC00567A">
            <TextBlock Text="Content 3" HorizontalAlignment="Center" Foreground="White" Margin="0,10,0,0"/>
        </Border>
    </controlskit:AdaptiveColumnsPanel>
</Page>