Align "RevisionQuery->needCommitPHIDs()" to use Edges, not the legacy table
Summary:
Depends on D20458. Ref T13276. Although I'm not thrilled about "needCommitPHIDs()", it has a few callers, including custom fields. Allow "need + attach + get" to survive for now since they're reasonably modern, at least.
However, use edges instead of "TABLE_COMMIT" and require `need...()` + `get...()`, removing the direct `load...()`.
Also remove `RevisionQuery->withCommitPHIDs(...)`, which has no callers.
Test Plan:
- Grepped for `loadCommitPHIDs` (only two hits, the private `RevisionQuery` method).
- Called "differential.getrevision", got commits.
- Viewed a revision, saw "Commits: ...".
- Grepped for `withCommitPHIDs()`, no callers on `RevisionQuery` (some other query classes have methods with this name).
- Called "differential.query", got commits.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13276
Differential Revision: https://secure.phabricator.com/D20459