The devtools flame chart includes a large number of unneeded widgets

There are a large number of empty Padding and SizedBox widgets in the flame chart. We should be able to optimize to eliminate all cases where we have 10 unneeded padding + sized boxes on a row without content. Technically we shouldn't need any padding or empty size boxes as the ExtentDelegateListView can define the spacing between widgets.

Fyi @kenzieschmoll