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