Summary:
Ref T8095. Render lint results in a future-ready way.
This makes the renderer accept `HarbormasterBuildLintMessage` objects. If we have legacy data instead, it converts it into `HarbormasterBuildLintMessage` objects.
Design is a bit rough but will be cleaned up later after T7739.
This moves away from "postponed linters", which are obsolete after Harbormaster (and were only ever used by Facebook).
Test Plan: {F523429}
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T8095
Differential Revision: https://secure.phabricator.com/D13377
e618b672d2