Update CHANGELOG.md for 12.9.0

[ci skip]

changelogs/unreleased/208453-add-title-to-analytics-sidebar-menus.yml

----
-title: Add title to Analytics sidebar menus
-merge_request: 26265
-author:
-type: added

changelogs/unreleased/208455-remove-analytics-suffixes-from-analytics-sidebar-menu-items.yml

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-title: Remove "Analytics" suffix from the sidebar menu items
-merge_request: 26415
-author:
-type: removed

changelogs/unreleased/208471-actionview-template-error-undefined-method-concat-for-nil-nilclass.yml

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-title: Fix an error with concat method
-merge_request:
-author:
-type: fixed

changelogs/unreleased/208473-fix-pipeline-tab-url.yml

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-title: Generate proper link for Pipeline tab
-merge_request: 26193
-author:
-type: fixed

changelogs/unreleased/208479-requests-for-svgs-returning-404-in-issues-analytics-feature.yml

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-title: 'Issue Analytics: Fix svg illustration path for empty state'
-merge_request: 26219
-author:
-type: fixed

changelogs/unreleased/208524-error-in-custom-dashboard-yml-file-breaks-the-dashboards-dropdown.yml

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-title: Fix dashboards dropdown if custom dashboard is broken
-merge_request: 26228
-author:
-type: fixed

changelogs/unreleased/208674-use-wh-acceleration-for-ui-project-import.yml

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-title: Use Workhorse acceleration for Project Import file upload via UI
-merge_request: 26278
-author:
-type: performance

changelogs/unreleased/208675-add-package_name-as-option-to-packages-api.yml

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-title: Added package_name as filter parameter to packages API
-merge_request: 26291
-author:
-type: added

changelogs/unreleased/208678-packages-project-and-group-api-will-return-processing-nuget-packag.yml

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-title: Fixed bug where processing NuGet packages are returned from the Packages API
-merge_request: 26270
-author:
-type: fixed

changelogs/unreleased/208788-fix-avg_cycle_analytics-giving-an-uncaught-error.yml

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-title: Fix avg_cycle_analytics uncaught error and optimize query
-merge_request: 26381
-author:
-type: fixed

changelogs/unreleased/208798-replace-instances-of-the-issue-duplicate-icon-with-the-duplicate-i.yml

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-title: Replace issue-duplicate icon with duplicate icon
-merge_request:
-author:
-type: other

changelogs/unreleased/208827-replace-issue-external-icon-with-external-link.yml

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-title: Replace issue-external icon with external-link
-merge_request: 208827
-author:
-type: other

changelogs/unreleased/208830-conan-package-reference-fix.yml

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-title: Fix package file finder for conan packages with a conan_package_reference filter
-merge_request: 26240
-author:
-type: fixed

changelogs/unreleased/208830-download-urls-conan-reference.yml

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-title: Fix Conan package download_urls and snapshot to return files based on requested
-  conan_package_reference
-merge_request: 27250
-author:
-type: fixed

changelogs/unreleased/208885-optimize-ci_pipeline-counters-related-to-the-ci-pipeline.yml

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-title: Optimize ci_pipelines counters in usage data
-merge_request: 26774
-author:
-type: performance

changelogs/unreleased/208886-optimize-deployment-counters-related-to-the-deployment.yml

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-title: Optimize Deployment related counters
-merge_request: 26757
-author:
-type: performance

changelogs/unreleased/208887-optimize-project-counters-mirrored-pipelines.yml

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-title: Optimize Project counters with pipelines enabled counter
-merge_request: 26802
-author:
-type: performance

changelogs/unreleased/208887-optimize-project-counters-projects_with_repositories_enabled.yml

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-title: Optimize Project counters with respository enabled counter
-merge_request: 26698
-author:
-type: performance

changelogs/unreleased/208887-optimize-project-counters-service-desk.yml

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-title: Optimize Project related count service desk enabled
-merge_request: 27115
-author:
-type: performance

changelogs/unreleased/208887-optimize-project-counters-with-slack-service.yml

----
-title: Optimize Project related count with slack service
-merge_request: 26686
-author:
-type: performance