Layout Explorer should maintain aspect ratio

STEPS TO REPRODUCE
1. Create a new app using the "skeleton" template.
2. Run it.
3. In the widget inspector, click on one of the ListTiles.

EXPECTED RESULTS
I would have expected to see a horizontal rectangle, with the aspect ratio of the list tile.

ACTUAL RESULTS
The visualization is sized to fit the screen, so even though it is labeled as "h=56" and "w=411.4", the box is actually taller than it is wide.

This gets worse e.g. when you tap the CircleAvatar widget, which is square (actually circular) in the real rendering, but appears like a vertical box in the widget inspector.

I think that, within reason, the aspect ratio of the child being displayed in the widget inspector should match the real aspect ratio. That would help orient the developer.

Reproduce the issue with a new app from the "skeleton" template, then open the widget inspector and Layout Explorer for a ListTile and CircleAvatar. Trace the Layout Explorer rendering from that entry point; done means displayed children preserve their real aspect ratios within the available screen space.

Written by the indexing model from the issue text.