Remove Controller->getHandle() and Controller->loadHandles()

Summary: Ref T7689. Modernize all callsites of these methods.

Test Plan:

• Poked at dashboards.
  • Pretty sure this code is technically unreachable right now.
• Viewed commit; viewed "Audit Status".
• Viewed a fund; viewed "Payable to"; viewed "Owner".
• Viewed herald rules; viewed "Author"; viewed "Applies To".
• Viewed a Legalpad document; viewed "Contributors".
• Viewed Phame post list; viewed blog; viewed post (viewed "Blog", viewed "Blogger").
• Viewed a macro; viewed "Audio".
• Viewed a Phriction page; viewed "Last Author".
• Viewed a Ponder question; viewed "Author".
• Viewed a Ponder answer; viewed header.
  • Behavior changed very slightly here; whatevs.
• Viewed a Countdown; viewed "Author".

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7689

Differential Revision: https://secure.phabricator.com/D12210