Add an acceptance test for Celerity maps

Summary: Fixes T5374. Add an acceptance test to the PhabricatorInfrastructureTestCase class which fails if a Celerity map is not up-to-date. In order to achieve this, a lot of code used to generate Celerity maps was transferred from CelerityManagementMapWorkflow to CelerityResourceMap and CelerityResourceMapGenerator.

Test Plan: Ran arc unit and noticed that all tests passed. Modified a JavaScript file and ran arc unit again (without running ./bin/celerity map)... this time the test failed, as expected.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T5374

Differential Revision: https://secure.phabricator.com/D9817