Convert `bin/files` to ObjectQuery

Summary: Ref T603. This has some custom logic which ObjectQuery can now perform more simply and more correctly.

Test Plan: Ran `bin/files purge F1`, `bin/files purge D1`, `bin/files purge --all`.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7180