Update CHANGELOG.md for 9.0.0

[ci skip]

changelogs/unreleased/22645-add-discussion-contribs-to-calendar.yml

----
-title: Add discussion events to contributions calendar
-merge_request: 8821
-author:

changelogs/unreleased/22818-licence-gitignore-and-yml-endpoints-removal.yml

----
-title: V3 deprecated templates endpoints removal
-merge_request: 8853
-author:

changelogs/unreleased/22951-fix-todos-api-endpoint-error-for-commits.yml

----
-title: Add spec for todo with target_type Commit
-merge_request: 9351
-author: George Andrinopoulos

changelogs/unreleased/23061-consolidate-project-lists.yml

----
-title: 'API: Consolidate /projects endpoint'
-merge_request: 8962
-author:

changelogs/unreleased/23062-allow-git-log-to-accept-follow-and-skip.yml

----
-title: Make Git history follow renames again by performing the --skip in Ruby
-merge_request:
-author:

changelogs/unreleased/23104-remove-public-param-for-projects.yml

----
-title: 'API: remove `public` param for projects'
-merge_request: 8736
-author:

changelogs/unreleased/23535-folders-in-wiki-repository.yml

----
-title: Show directory hierarchy when listing wiki pages
-merge_request: 8133
-author: Alex Braha Stoll

changelogs/unreleased/23819-fix-milestone-counters-to-top-right-of-panel-headings.yml

----
-title: Fix position of counter in milestone panels
-merge_request: 7842
-author: Andrew Smith (EspadaV8)

changelogs/unreleased/23948-assign-to-me.yml

----
-title: Re-add Assign to me link to Merge Request and Issues
-merge_request:
-author:

changelogs/unreleased/23993-drop-ci_projects.yml

----
-title: Drop unused ci_projects table and some unused project_id columns,
-  then rename gl_project_id to project_id. Stop exporting job trace when
-  exporting projects.
-merge_request: 9378
-author: David Wagner

changelogs/unreleased/24333-close-issues-with-merge-request-title-ui.yml

----
-title: Show Issues mentioned / being closed from a Merge Requests title below the
-  'Accept Merge Request' button
-merge_request: 9194
-author: Jan Christophersen

changelogs/unreleased/24683-sidebar-spinners.yml

----
-title: hide loading spinners for server-rendered sidebar fields
-merge_request:
-author:

changelogs/unreleased/24976-start-of-line-mention.yml

----
-title: Added a feature to create a 'directly addressed' Todo when mentioned in the beginning of a line.
-merge_request: 7926
-author: Ershad Kunnakkadan

changelogs/unreleased/24998-fix-typo-gitlab-config-file.yml

----
-title: Fix typo in Gitlab config file
-merge_request: 9702
-author: medied

changelogs/unreleased/25367-add-impersonation-token.yml

----
-title: Manage user personal access tokens through api and add impersonation tokens
-merge_request: 9099
-author: Simon Vocella

changelogs/unreleased/25437-just-emoji.yml

----
-title: Introduce /award slash command; Allow posting of just an emoji in comment
-merge_request: 9382
-author: mhasbini

changelogs/unreleased/25465-todo-done-clicking-is-kind-of-unsafe.yml

----
-title: Todo done clicking is kind of unusable
-merge_request: 8691
-author: Jacopo Beschi @jacopo-beschi

changelogs/unreleased/25503_issues_finder_performance.yml

----
-title: Filter by projects in the end of search
-merge_request: 9030
-author:

changelogs/unreleased/25709-diff-file-overflow.yml

----
-title: Responsive title in diffs inline, side by side, with and without sidebar
-merge_request: 8475
-author:

changelogs/unreleased/25920-create-issue-from-failing-build.yml

----
-title: Add button to create issue for failing build
-merge_request: 9391
-author: Alex Sanford