R1:99be132ea21e

Allow public users to make intracluster API requests

Summary:
Ref T10784. On `secure`, logged-out users currently can't browse repositories when cluster/service mode is enabled because they aren't permitted to make intracluster requests.

We don't allow totally public external requests (they're hard to rate limit and users might write bots that polled `feed.query` or whatever which we'd have no way to easily disable) but it's fine to allow intracluster public requests.

Test Plan: Browsed a clustered…