remove API calls from CE to CI

CHANGELOG

app/controllers/ci/projects_controller.rb

app/models/ci/project.rb

app/models/project_services/gitlab_ci_service.rb

app/services/ci/create_project_service.rb

app/services/projects/fork_service.rb

app/workers/fork_registration_worker.rb

config/routes.rb

doc/ci/api/README.md

doc/ci/api/forks.md

features/steps/project/services.rb

lib/ci/api/api.rb

lib/ci/api/forks.rb

spec/controllers/ci/projects_controller_spec.rb

spec/lib/gitlab/backend/grack_auth_spec.rb

spec/models/project_services/gitlab_ci_service_spec.rb

spec/requests/api/projects_spec.rb

spec/requests/api/services_spec.rb

spec/requests/ci/api/forks_spec.rb

spec/services/ci/create_project_service_spec.rb