Have Badges use getMostOpenPolicy for View
Summary: Fixes T8938. Sets by default for new badges, getMostOpenPolicy. Removes ability to edit viewPolicy.
Test Plan: Create a new badge, see its public, assign it, log out, still able to view it.
Reviewers: btrahan, epriestley
Reviewed By: btrahan
Subscribers: epriestley, Korvin
Maniphest Tasks: T8938
Differential Revision: https://secure.phabricator.com/D13702