Use ConstraintLayout for theme preview to fix UI break of largest font/display size

Before:
- Normal https://screenshot.googleplex.com/15MgPxRCzUJ.png
- Largest font and display size https://screenshot.googleplex.com/daDFBMxP0Ve.png
- Largest font and display size full preview https://screenshot.googleplex.com/gUWvARts7zS.png

After:
- Normal https://screenshot.googleplex.com/5FSUE7GLTZ0.png
- Largest font and display size https://screenshot.googleplex.com/ZaRf2pzRCjD.png
- Largest font and display size full preview https://screenshot.googleplex.com/R3iFjjWYTYC.png

Next: Update the UI to match new spec once we have, new spec is tracked by b/157097884

Test: Manually
Bug: 157402935
Change-Id: I0d202146f2be258acb923965ede6fac93bf5fc48