Prevent status updates from getting cut off on contact tiles

- When font size is extra large (for accessibility), the status
message on the contact tiles can get cut off.

- Use sp instead of dip for the height of the black
shadowbox so that it can scale when the font size is increased.
See https://android-git.corp.google.com/g/#/c/137302/
Note: this technique should only be done sparingly as advised
by the framework team

- Remove list view divider on contact tiles in group detail
fragment

Bug: 5324851
Bug: 5221058
Change-Id: I1db02198ebf1a8bd0bd7552bf1900030444cef3c