Use short label, request title and request description for roles.

This change allows the request role dialog to make use of the new
request title and request description strings, as well as changing the
label use for a role to short label in role lists. Showing role
description in the new Settings UI will come in another upcoming CL.

Bug: 128713569
Test: manual
Change-Id: If2dd85a94ec7e450eda1b1d28d775f265788f203