Merge branch 'pedropombeiro/rename-runner_fleet' into 'master'

Rename runner_fleet category to fleet_visibility

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/138621



Merged-by: Vladimir Shushlin <vshushlin@gitlab.com>
Approved-by: Miguel Rincon <mrincon@gitlab.com>
Approved-by: Eulyeon Ko <5961404-euko@users.noreply.gitlab.com>
Approved-by: Serena Fang <sfang@gitlab.com>
Approved-by: Vladimir Shushlin <vshushlin@gitlab.com>
Reviewed-by: Pedro Pombeiro <noreply@pedro.pombei.ro>
Reviewed-by: Eulyeon Ko <5961404-euko@users.noreply.gitlab.com>
Co-authored-by: Pedro Pombeiro <noreply@pedro.pombei.ro>