Improve visual designer layout tools

Add tools to the visual designer to help with laying out controls. There should be a toolbar at the top of the visual designer view with buttons for:

• View in light/dark mode
• Lock current control(s)
• Show points measurements when dragging
• Show tab order
• Order forward/order backward/bring to front/send to back
• Fill height
• Fill width
• Align control left/right/top/bottom
• Space collection of controls horizontally/vertically