Make policy violation dialog more flexible

Summary:
Ref T8424. When users are rejected because they can't see the space an object is in, this isn't really a capability rejection. Don't require a capability when rejecting objects.

This mostly simplifies upcoming changes.

Test Plan:

• Viewed a capability exception dialog, it looked the same as always.
• (After additional changes, viewed a space exception dialog.)

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8424

Differential Revision: https://secure.phabricator.com/D13155