R1:6ff5eed20656

Fix visibility of `DiffusionLowLevelQuery::executeQuery()` methods

Summary: Ref T6822.

Test Plan: `grep`

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T6822

Differential Revision: https://secure.phabricator.com/D11411