Homestyx hydra

R1:b8f6248e0782

Fix an issue where handles could load with the incorrect viewer when building mail about changes to related objects

Summary:
See <https://phabricator.wikimedia.org/T179591>. Some time ago, all handle rendering preloaded handles: things emitted a list of PHIDs they'd need handles for, then later used only those PHIDs.

Later, we introduced `HandlePool` and lazy/on-demand handle loading. Modern transactions mostly use this to render object PHIDs.

When we build mail, many newer transactions use an on-demand…
Repository: R1 hydra
Commit Date: May 21 2019