DEV: Remove unsafe-eval from development CSP (#8569)

- Refactor source_url to avoid using eval in development
- Precompile handlebars in development
- Include template compilers when running qunit
- Remove unsafe-eval in development CSP
- Include unsafe-eval only for qunit routes in development

test/javascripts/test_helper.js

@@ -3,9 +3,7 @@
 //= require env
 //= require jquery.debug
 //= require jquery.ui.widget
-//= require handlebars
 //= require ember.debug
-//= require ember-template-compiler
 //= require message-bus
 //= require qunit/qunit/qunit
 //= require ember-qunit
@@ -26,6 +24,11 @@
 //= require application
 //= require admin
 
+// These are not loaded in prod or development
+// But we need them for testing handlebars templates in qunit
+//= require handlebars
+//= require ember-template-compiler
+
 //= require sinon/pkg/sinon
 
 //= require helpers/assertions