Add in more model changes around execution environments

- a new unique name field to EE
- a new configure-Tower-in-Tower setting DEFAULT_EXECUTION_ENVIRONMENT
- an Org-level execution_environment_admin_role
- a default_environment field on Project
- a new Container Registry credential type
- order EEs by reverse of the created timestamp
- a method to resolve which EE to use on jobs

awx/main/models/rbac.py

@@ -40,6 +40,7 @@ role_names = {
     'inventory_admin_role': _('Inventory Admin'),
     'credential_admin_role': _('Credential Admin'),
     'job_template_admin_role': _('Job Template Admin'),
+    'execution_environment_admin_role': _('Execution Environment Admin'),
     'workflow_admin_role': _('Workflow Admin'),
     'notification_admin_role': _('Notification Admin'),
     'auditor_role': _('Auditor'),
@@ -60,6 +61,7 @@ role_descriptions = {
     'inventory_admin_role': _('Can manage all inventories of the %s'),
     'credential_admin_role': _('Can manage all credentials of the %s'),
     'job_template_admin_role': _('Can manage all job templates of the %s'),
+    'execution_environment_admin_role': _('Can manage all execution environments of the %s'),
     'workflow_admin_role': _('Can manage all workflows of the %s'),
     'notification_admin_role': _('Can manage all notifications of the %s'),
     'auditor_role': _('Can view all aspects of the %s'),