Move most of AddBuilds to hydra-eval-jobset

Having this stuff in a separate module is a remnant of the time when
hydra-server could add builds to the queue directly. This is no longer
the case.

src/lib/Hydra/Controller/API.pm

@@ -5,7 +5,6 @@ use strict;
 use warnings;
 use base 'Hydra::Base::Controller::REST';
 use Hydra::Helper::Nix;
-use Hydra::Helper::AddBuilds;
 use Hydra::Helper::CatalystUtils;
 use Hydra::Controller::Project;
 use JSON;