Add latest changes from gitlab-org/gitlab@12-7-stable-ee

changelogs/unreleased/fix-on-train-method-in-mr.yml

----
-title: Fix RefreshMergeRequestsService raises an exception and unnecessary sidekiq retry
-merge_request: 22262
-author:
-type: fixed

changelogs/unreleased/fix-prometheus-network-connectivity-error.yml

----
-title: Return 503 error when metrics dashboard has no connectivity
-merge_request: 22140
-author:
-type: fixed

changelogs/unreleased/fix-skip-snippet-raw-buttons-for-external-caching.yml

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-title: Exclude snippets from external caching handling
-merge_request:
-author:
-type: fixed

changelogs/unreleased/fj-add-migrations-snippet-repository.yml

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-title: Add migrations for version control snippets
-merge_request: 22275
-author:
-type: added

changelogs/unreleased/generate-sample-metrics-intervals.yml

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-title: Generate Prometheus sample metrics over pre-set intervals
-merge_request: 22066
-author:
-type: added

changelogs/unreleased/gitaly-cache-invalidator-ff.yml

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-title: Add back feature flag for cache invalidator
-merge_request: 22106
-author:
-type: changed

changelogs/unreleased/gitaly-version-v1.79.0.yml

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-title: Upgrade to Gitaly v1.79.0
-merge_request: 22515
-author:
-type: changed

changelogs/unreleased/gitaly-version-v1.81.0.yml

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-title: Upgrade to Gitaly v1.81.0
-merge_request: 23198
-author:
-type: changed

changelogs/unreleased/himkp-27242.yml

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-title: 'Fix issue: Discard button in Web IDE does nothing'
-merge_request: 21902
-author:
-type: fixed

changelogs/unreleased/himkp-33441.yml

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-title: Stage all changes by default in Web IDE
-merge_request: 21067
-author:
-type: added

changelogs/unreleased/icons-to-alerts.yml

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-title: Fix aligment for icons on alerts
-merge_request: 22760
-author: Rajendra Kadam
-type: added

changelogs/unreleased/id-call-lfs-once-when-vue-file-list-enabled.yml

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-title: Execute Gitaly LFS call once when Vue file enabled
-merge_request: 22168
-author:
-type: performance

changelogs/unreleased/ide_render_whitespaces.yml

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-title: Render whitespaces in code
-merge_request: 17244
-author: Mathieu Parent
-type: added

changelogs/unreleased/improve-pipeline-processing.yml

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-title: Implement Atomic Processing that updates status of builds, stages and pipelines in one go
-merge_request: 20229
-author:
-type: performance

changelogs/unreleased/include-subgroups-in-group-search.yml

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-title: Include subgroups when searching inside a group
-merge_request: 22991
-author:
-type: fixed

changelogs/unreleased/issue-28822-add-style-to-no-commit-message.yml

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-title: Updated no commit verbiage
-merge_request: 22765
-author:
-type: other

changelogs/unreleased/issue_2030_2.yml

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-title: Process quick actions when using Service Desk templates
-merge_request: 21948
-author:
-type: fixed

changelogs/unreleased/jej-prevent-enabling-group-managed-accounts-when-SSO-not-linked.yml

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-title: Require group owner to have linked SAML before enabling Group Managed Accounts
-merge_request: 21721
-author:
-type: fixed

changelogs/unreleased/jl-bump-rack-cors-1-0-6.yml

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-title: Update rack-cors to 1.0.6
-merge_request: 22809
-author:
-type: security

changelogs/unreleased/jl-bump-rdoc-6-2.yml

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-title: Update rdoc to 6.1.2
-merge_request: 22434
-author:
-type: security