Change "lint save" to not use Arcanist Projects

Summary: Ref T7604. Change DiffusionLintSaveRunner to use repositories instead of Arcanist Projects.

Test Plan: Ran the save_lint.php script and queried results using the diffusion.getlintmessages Conduit endpoint.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T7604

Differential Revision: https://secure.phabricator.com/D12893