[Tizen] Support Vertical/HorizontalScrollStep to ScrollView

[rookiejava]

Description of Change

This PR is about supporting the scroll step (both vertical and horizontal) to move ScrollView by key event on Tizen. This can be especially useful when moving the scroll of the scroll view on a remote control keystroke based TV device. As you can see in the screenshot below, you can adjust the VerticalScrollStep to make the scroll view move smoother.

• Before (default)

• After (adjust the vertical scroll step properly)

Developers Guide

This Tizen platform-specific is used to set the scroll step to move ScrollView by key event. It can be consumed from XAML and C# as follows.

• XAML

<ContentPage ...
    xmlns:tizen="clr-namespace:Xamarin.Forms.PlatformConfiguration.TizenSpecific;assembly=Xamarin.Forms.Core">
    <ScrollView tizen:ScrollView.VerticalScrollStep="500">
        ....
    </ScrollView>
</ContentPage>

• C#

using Xamarin.Forms.PlatformConfiguration;
using Xamarin.Forms.PlatformConfiguration.TizenSpecific;
...

var scrollView = new Xamarin.Forms.ScrollView();
scrollView.On<Tizen>().SetHorizontalScrollStep(500); // set 
var step = scrollView.On<Tizen>().GetHorizontalScrollStep(); //get

Issues Resolved

None

API Changes

namespace Xamarin.Forms.PlatformConfiguration.TizenSpecific

Added:

• int ScrollView.VerticalScrollSize { get; set; } //Bindable Property
• int ScrollView.HorizontalScrollSize { get; set; } //Bindable Property

Platforms Affected

• Tizen

Behavioral/Visual Changes

None

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)