Add latest changes from gitlab-org/gitlab@master

.gitlab/ci/rails.gitlab-ci.yml

.gitlab/ci/rules.gitlab-ci.yml

.gitlab/issue_templates/Security developer workflow.md

Gemfile

Gemfile.lock

app/models/audit_event.rb

changelogs/unreleased/issue_11391_2.yml

...gs/unreleased/sh-feature-flag-persisted-process-cache.yml

db/migrate/20181016141739_add_status_to_deployments.rb

...190416185130_add_merge_train_enabled_to_ci_cd_settings.rb

...90416213615_add_variable_type_to_ci_pipeline_variables.rb

...grate/20190426180107_add_deployment_events_to_services.rb

db/migrate/20191023093207_add_comment_actions_to_services.rb

db/migrate/20200310132654_add_instance_to_services.rb

...grate/20200212052620_readd_template_column_to_services.rb

...on_noteable_type_and_noteable_id_to_sent_notifications.rb

db/schema.rb

doc/ci/variables/predefined_variables.md

doc/development/api_styleguide.md

doc/user/application_security/index.md