Add latest changes from gitlab-org/gitlab@12-5-stable-ee

changelogs/unreleased/show-prometheus-is-updating.yml

...nreleased/sort-vulnerabilities-for-pipeline-dashboard.yml

changelogs/unreleased/stein_ma-gitlab-patch-32.yml

changelogs/unreleased/tr-remove-grafana-ff.yml

changelogs/unreleased/tracking-experimental-signup-flow.yml

.../unreleased/update-gitlab-runner-helm-chart-to-0-10-0.yml

.../unreleased/update-gitlab-runner-helm-chart-to-0-10-1.yml

changelogs/unreleased/update-pages-1-12.yml

changelogs/unreleased/visual-review-api.yml

changelogs/unreleased/zj-pg-connection-ff-gitaly.yml