Add new res for small screens in avatar picker

This CL adds a dimens file for smaller screens to avoid the avatar
picker images being cropped.

Screenshot: https://screenshot.googleplex.com/4AcJTr3TTDJ3yc4.png

Bug: 238380225
Test: manual check screen on various screen sizes
Change-Id: I84478030145cadb9930989f0c077f2343fe36fe1