Improve Columns Collection to work with XAML Hot Reload

[w-ahmad]

Closes #20

This PR improves TableViewColumnsCollection to work with XAMLHot Reload by inheriting from DependencyObjectCollection. A new interface ITableViewColumnsCollection is added to use as a contract for the TableViewColumnsCollection, it is necessary to force the InteliSence to only show TableViewColumns when adding columns from the XAML.

Here is the new implementation:

// Interface with some other properties like 'TableView', 'VisibleColumns'
public interface ITableViewColumnsCollection : IList<TableViewColumn>, INotifyCollectionChanged {  }

// Implementation
public partial class TableViewColumnsCollection : DependencyObjectCollection, ITableViewColumnsCollection {  }

// Actual Columns property in TableView
public ITableViewColumnsCollection Columns { get; }

Limitations:

It seems that WinUI3 cannot update properties of type Binding with XAML hot reload, so the TableViewBoundColumn.Binding property won't reflect any changes made in XAML.

[w-ahmad]

Thank you so much @michael-hawker for your support to make this happen. Just a small hickup, the Binding properties of the columns are not useful through the Xaml editor due to a bug in WinUI3.

microsoft/microsoft-ui-xaml#10719