Build "DiffusionCommitRef" objects from "internal.commit.search", not "diffusion.querycommits", in the message parser worker

Summary: Ref T13552. Swap the call we're using to build "CommitRef" objects here to the recently-introduced "internal.commit.search" method.

Test Plan: Used "bin/repository reparse --message ..." to reparse commits, added "var_dump()" to inspect results. Saw sensible CommitRef and CommitData objects get built.

Maniphest Tasks: T13552

Differential Revision: https://secure.phabricator.com/D21446