Create a new `Bar` view to replace `StatusBar` (and eventually `MenuBar`)

[tig]

Possible dupe of:

• Modernize Menu - Base on Bar and address litany of issues #2975

I want to refactor StatusBar. It's actually a quite simple control, but was written before...

• View.Text
• View.HotKey with killer ToString support
• Frames (for StatusItem spacing/alignment)
• Consistency in eventing (KeyBindings and no Action).
• KeyBindingScope.Application

It should just be a View that is Width = Fill and Y = AnchorEnd by default.

The new StatusItem:

public class StatusItem : View {
    public override Text {
        get => $"KeyBindings.FirstOrDefault(b => b.Scope != KeyBindingScope.Focus).GetKeyFromCommands(Commands.Default));
}

... plus some stuff to auotmatically enable / disable Border.Thickness = new Thickness (0, 0, 1, 0) for the separator.

StatusBar.Add is an override that sets subview.X appropriately (1st gets X = 0, subsequent get X = Pos.View(prev); last gets Width = Dim.Fill()).

Originally posted by @tig in #3070 (comment)

[BDisp]

The user needs to create a format Title to be able to prefix the shortcut. I think this should be the responsibility of the StatusBar generating the formatted string when redrawing. The current advantage is that the user can create a custom string for the shortcut, such as "~^A~ Add" for Ctrl+A. But the user may make a mistake by creating a different customization of the Shortcut property. The problem with this behavior is that the Title property will also return the shortcut when the user intends to obtain only the string "Add".
My question is whether it would be better for the StatusBar to automatically generate the string when redrawing, joining the Shortcut and the Title, just like the MenuBar, or leave it as is?