Redirect `threat_monitoring/policies` routes to `policies_controller` routes and delete associated actions

Summary

• with the removal of the :security_orchestration_policies_configuration feature flag, the /-/threat_monitoring/policies/new and /-/threat_monitoring/policies/edit routes are no longer used and should be removed

Improvements

• backend redirect the policies endpoints in at https://gitlab.com/gitlab-org/gitlab/blob/master/ee/config/routes/project.rb#L44 to the the policies endpoints at https://gitlab.com/gitlab-org/gitlab/blob/master/ee/config/routes/project.rb#L62 and
  • update/delete any associated code and tests
• backend remove the threat_monitoring#edit and threat_monitoring#new actions and any associated templates and tests

Risks

If done before the feature flag is removed, it will prevent us from rolling the feature flag back in the event of an issue

Involved components

Modify the following files

• https://gitlab.com/gitlab-org/gitlab/blob/master/ee/config/routes/project.rb#L44
• https://gitlab.com/gitlab-org/gitlab/blob/master/ee/app/controllers/projects/threat_monitoring_controller.rb#L21
• https://gitlab.com/gitlab-org/gitlab/blob/master/ee/app/helpers/policy_helper.rb#L4 (delete policy_details helper as it is no longer used)

Delete the following files

• https://gitlab.com/gitlab-org/gitlab/blob/master/ee/app/views/projects/threat_monitoring/edit.html.haml
• https://gitlab.com/gitlab-org/gitlab/blob/master/ee/app/views/projects/threat_monitoring/new.html.haml
• https://gitlab.com/gitlab-org/gitlab/blob/master/ee/app/assets/javascripts/pages/projects/threat_monitoring/edit/index.js
• https://gitlab.com/gitlab-org/gitlab/blob/master/ee/app/assets/javascripts/pages/projects/threat_monitoring/new/index.js