(meta) Merge request approvals

Part of

(meta) GitLab discussion product development https://gitlab.com/gitlab-org/gitlab-ce/issues/24688

Issues

• 8.16 #1262 (closed) View people who have approved merge request
• 8.16 #894 (closed) Remove approval in merge request
• 8.16 #1287 (closed) View system notes for merge request approval and approval removal
• 8.16 #1288 (closed) Receive notification emails for merge request approval and approval removal
• #1593 (closed) Approval suggestions dropdown seems to include all GitLab users
• #1594 (closed) Cryptic validation error when creating MR with approvers while approvals have been disabled
• #1526 (closed) Suggest approvers in merge request - UX improvements
• #1126 (closed) Approve a merge request beyond the number of required approvals
• #1388 (closed) Approvals functionality after a merge request has been merged
• #499 Suggest MR reviewers based on a blame of the modified code
• #1073 (closed) Suggest approval based on code authority
• #769 (closed) Access multiple merge requests that need attention based on approvals information
• #582 (closed) Disallow overwriting approvers when creating a MR
• #460 (closed) Per branch merge request approvals
• #761 (closed) Block merge request with a negative approval signal
• #885 (closed) Add API for managing merge request templates and approvers
• #965 (closed) Upgrading approvals with approval chain