Move SSHKey table to Auth database

Summary: Ref T5833. Since these will no longer be bound specifically to users, bring them to a more central location.

Test Plan:
  - Edited SSH keys.
  - Ran `bin/ssh-auth` and `bin/ssh-auth-key`.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5833

Differential Revision: https://secure.phabricator.com/D10791

src/applications/auth/query/PhabricatorAuthSSHKeyQuery.php

@@ -24,7 +24,7 @@ final class PhabricatorAuthSSHKeyQuery
   }
 
   protected function loadPage() {
-    $table = new PhabricatorUserSSHKey();
+    $table = new PhabricatorAuthSSHKey();
     $conn_r = $table->establishConnection('r');
 
     $data = queryfx_all(