Support 'Panel position' setting under 'Customize layout' button

[abhijit-chikane]

Right now, VS Code only supports showing/hiding the panel through the 'Customize layout' popup
but as we can place this panel at the top, right, left, and bottom 
I would like to see this setting available under the existing 'Customize layout' popup just like 'Primary sidebar position'

Also, one more improvement we need in this area
If I move my primary sidebar to the right it reflects that thing in this layout by showing the proper icon

but for panel, it does not reflect the existing panel position
it always shows me this icon even though I have set it up on the left

maybe we need some UX input for showcasing the panel and sidebar with some different indicators

[benibenj]

@daviddossett thoughts on adding Panel Position section in here? I assume it's not already in the Layout dropdown to keep he options short and simple. Adding 4 more options causes the dropdown to scroll.

Maybe there should be a More... entry at the bottom which then reveals more customizable options?

Also, we might need to have panel top (on & off) icons since the panel can now be moved to the top, above the editor area.