Remove some ad-hoc handle loads from Releeph

Summary:
Ref T3551. Releeph does a bunch of old-school on-object data loading; start cleaning that up.

This doesn't change anything, just makes the code more modern/consistent.

Test Plan: Edited a request; called `releephwork.nextrequest`.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T3551

Differential Revision: https://secure.phabricator.com/D8819