Refine the IllustrationPreference.

- If we set a fixed height for the illustration and automatically
  scale the width of the illustration, the size of the background
  layer will be different from the size of the illustration. To
  fix this problem, we must make the background layer the same
  size as the illustration and automatically scale.
- Update the size of background to 412x300.
- Update the layout of frame's child views to wrap_content.
- Update the padding of frame to 16dp.

Bug: 190810977
Test: robotest and see the UI

Change-Id: I0422f91c24860154fea7c766d5670c314d62bebb