Update CHANGELOG.md for 12.3.0

[ci skip]

changelogs/unreleased/66402-use-visual-review-tools-npm-package.yml

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-title: Move visual review toolbar code to NPM
-merge_request: 32159
-author:
-type: fixed

changelogs/unreleased/66443-unrecoverable-configuration-loop-in-external-auth-control.yml

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-title: Don't check external authorization when disabling the service
-merge_request: 32102
-author: Robert Schilling
-type: fixed

changelogs/unreleased/66454-base-components.yml

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-title: Creates base components for the new job log
-merge_request:
-author:
-type: added

changelogs/unreleased/66454-utils-parser.yml

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-title: Creates utility parser for the job log
-merge_request: 32555
-author:
-type: added

changelogs/unreleased/66467-enable-error-tracking-only-user-can-read-sentry-logs.yml

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-title: Display `more information` docs link on error tracking page when users do not have permissions to enable that feature
-merge_request: 32365
-author: Romain Maneschi
-type: fixed

changelogs/unreleased/66524-issue-due-notification-emails-are-threaded-incorrectly.yml

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-title: Fix issue due notification emails not being threaded correctly
-merge_request: 32325
-author:
-type: fixed

changelogs/unreleased/66616-follow-up-documentation-for-merge-trains-cancel-when-running.yml

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-title: Update merge train documentation
-merge_request: 32218
-author:
-type: changed

changelogs/unreleased/66637-use-chronic-duration-in-thread-safe-way.yml

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-title: Use `ChronicDuration` in a thread-safe way
-merge_request: 32817
-author:
-type: fixed

changelogs/unreleased/66701-done-quick-action-is-available-even-no-To-Do-exists.yml

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-title: Changed todo/done quick actions to work not only for first usage
-merge_request: 16837
-author: Marc Schwede
-type: fixed

changelogs/unreleased/66715-delete-search-animation.yml

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-title: delete animation width on global search input
-merge_request: 32399
-author: Romain Maneschi
-type: other

changelogs/unreleased/66986-milestone-release-many-to-many.yml

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-title: Switch Milestone and Release to a many-to-many relationship
-merge_request: 16517
-author:
-type: changed

changelogs/unreleased/67037-user-content-gitlab-static-net-brings-back-404-only.yml

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-title: Default the asset proxy whitelist to the installation domain
-merge_request: 32703
-author:
-type: fixed

changelogs/unreleased/67248-snippet-title-whitespace.yml

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-title: Add bottom margin to snippet title
-merge_request: 32877
-author:
-type: fixed

changelogs/unreleased/ab-add-index-for-ci-builds-metrics.yml

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-title: Create partial index for gitlab-monitor CI metrics
-merge_request: 32546
-author:
-type: performance

changelogs/unreleased/ab-admin-page-user-active-count.yml

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-title: Replace indexes for counting active users
-merge_request: 32538
-author:
-type: performance

changelogs/unreleased/ab-partial-events-index.yml

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-title: Replace events index with partial one
-merge_request: 32874
-author:
-type: performance

changelogs/unreleased/ab-partial-index-for-namespaces-type.yml

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-title: Partial index for namespaces.type
-merge_request: 32876
-author:
-type: performance

changelogs/unreleased/ab-remove-support-bot-column.yml

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-title: Remove Users.support_bot column
-merge_request: 32554
-author:
-type: other

changelogs/unreleased/ab-routable-nplus1.yml

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-title: Preload routes information to fix N+1 issue
-merge_request: 32352
-author:
-type: performance

changelogs/unreleased/ab-unconfirmed-email-index.yml

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-title: Create index for users.unconfirmed_email
-merge_request: 32664
-author:
-type: performance