Update the widget previews to use the container sizes

Additionally, adjusts the margins on sides, to make space for displaying
multiple previews side by side.

As a result of this change, previews aren't cropped anymore (indirectly
also fixing b/317366201).

There is one more follow up pending - to limit the height of
recommendations in two pane sheet to only visible area to keep the
suggestions quick to look and concise. It will also help with better
scroll experience when size is same across pages.

* http://screencast/cast/NTQ0Njc4ODgyNjc5MTkzNnxjYzZiYTU2Ny02Yw
* http://screencast/cast/NTk4ODMyMDkxOTE1ODc4NHw3NzdlNTgxZS1kMw
* http://screencast/cast/NTYxOTc5NjIxNjM4MTQ0MHxiMjQ2Njc3OC0zOQ
* http://screencast/cast/NDk4MjIxNjI0MDEzNjE5MnxjY2IwYmIxNi00Mw

Bug: 319152349
Flag: N/A
Test: Image test and table utils test
Change-Id: I07465bd4d84597b560a2b998ff1ccbf9867c0192