restore custom proficiency colors to speedgrader rubrics

closes OUT-3676
flag=none

Test plan:
- without custom outcome proficiency ratings, create
  an assignment with an outcome-based rubric
- in speedgrader, verify that choosing different rubric cells
  uses default colors
- add custom proficiency ratings at /accounts/self/rubrics
- in speedgrader, verify that choosing different rubric cells
  uses the customized colors

Change-Id: I772c5c57e11ede5053aaeaa11f4e7d24db25bceb
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/239123
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Pat Renner <prenner@instructure.com>
Reviewed-by: Augusto Callejas <acallejas@instructure.com>
QA-Review: Adam Lenning <adam.lenning@instructure.com>
Product-Review: Michael Brewer-Davis <mbd@instructure.com>

app/controllers/gradebooks_controller.rb

@@ -886,7 +886,8 @@ class GradebooksController < ApplicationController
           assignment_title: @assignment.title,
           rubric: rubric ? rubric_json(rubric, @current_user, session, style: 'full') : nil,
           nonScoringRubrics: @domain_root_account.feature_enabled?(:non_scoring_rubrics),
-          outcome_extra_credit_enabled: @context.feature_enabled?(:outcome_extra_credit),
+          outcome_extra_credit_enabled: @context.feature_enabled?(:outcome_extra_credit), # for outcome-based rubrics
+          outcome_proficiency: outcome_proficiency, # for outcome-based rubrics
           group_comments_per_attempt: @assignment.a2_enabled?,
           can_comment_on_submission: @can_comment_on_submission,
           show_help_menu_item: show_help_link?,

spec/controllers/gradebooks_controller_spec.rb

@@ -2385,6 +2385,12 @@ describe GradebooksController do
         expect(js_env.fetch(:filter_speed_grader_by_student_group_feature_enabled)).to be false
       end
 
+      it "sets outcomes keys" do
+        get 'speed_grader', params: {course_id: @course, assignment_id: @assignment.id}
+        expect(js_env).to have_key :outcome_proficiency
+        expect(js_env).to have_key :outcome_extra_credit_enabled
+      end
+
       describe "student group filtering" do
         before(:each) do
           @course.root_account.enable_feature!(:filter_speed_grader_by_student_group)