Merge "Use ConstraintLayout for theme preview to fix UI break of largest font/display size" into ub-launcher3-master am: aaa81e46f0

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/ThemePicker/+/11596388

Change-Id: I26fb5b261b9a5dd2f22a11909e9e61a177f6fb1d