Reinstitute a core `manual` status for manual actions

app/models/ci/build.rb

app/models/ci/pipeline.rb

app/models/commit_status.rb

app/models/concerns/has_status.rb

app/services/ci/process_pipeline_service.rb

app/views/projects/ci/builds/_build.html.haml

lib/gitlab/ci/status/manual.rb

lib/gitlab/data_builder/pipeline.rb

spec/models/ci/build_spec.rb

spec/services/ci/process_pipeline_service_spec.rb