Add latest changes from gitlab-org/gitlab@master

Gemfile

Gemfile.lock

app/assets/javascripts/issuable_form.js

...avascripts/pipelines/components/graph/graph_component.vue

...avascripts/pipelines/components/graph/linked_pipeline.vue

...ts/pipelines/components/graph/linked_pipelines_column.vue

app/assets/stylesheets/pages/pipelines.scss

...ogs/unreleased/194764-fix-resolve-thread-in-new-issue.yml

changelogs/unreleased/195137-update-webpack-to-4-41-5.yml

...gs/unreleased/parent-child-upstream-downstream-labels.yml

doc/ci/junit_test_reports.md

doc/development/fe_guide/style/vue.md

doc/user/project/integrations/prometheus_library/nginx.md

locale/gitlab.pot

package.json

spec/frontend/pipelines/graph/linked_pipeline_spec.js

spec/frontend/pipelines/graph/linked_pipelines_mock_data.js

spec/javascripts/pipelines/graph/graph_component_spec.js

...vascripts/pipelines/graph/linked_pipelines_column_spec.js

spec/javascripts/pipelines/linked_pipelines_mock.json