Merge branch '519316-fork-suggestion-becomes-page-level-alert' into 'master'

Fork suggestion becomes a modal

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/182881



Merged-by: Stanislav Lashmanov <slashmanov@gitlab.com>
Approved-by: Chaoyue Zhao <czhao@gitlab.com>
Approved-by: Brendan Lynch <blynch@gitlab.com>
Approved-by: Stanislav Lashmanov <slashmanov@gitlab.com>
Reviewed-by: Stanislav Lashmanov <slashmanov@gitlab.com>
Reviewed-by: Chaoyue Zhao <czhao@gitlab.com>
Reviewed-by: GitLab Duo <gitlab-duo@gitlab.com>
Reviewed-by: Alyssa Trinh <atrinh@gitlab.com>
Co-authored-by: psjakubowska <psedlak-jakubowska@gitlab.com>