R1:facd3ea8ef5a

Modernize chatlog a bit

Summary:
Ref T4786. This doesn't fully fix the issue since there's no way to make channels public yet, but gets some of the infrastructure more up to date.

- Allow public access to the list and log controllers.
- Implement proper policy checks in the Events (this has no practical impact on the only controller that loads this stuff, it's just for general/future purposes).
- Remove a old-style unused method for building page frames.

Test Plan: Viewed log list and log details…