Move downstream pipeline rate limit to application setting

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/144077



Merged-by: Furkan Ayhan <furkanayhn@gmail.com>
Approved-by: James Nutt <jnutt@gitlab.com>
Approved-by: Max Orefice <morefice@gitlab.com>
Approved-by: Briley Sandlin <bsandlin@gitlab.com>
Approved-by: Olena Horal-Koretska <ohoralkoretska@gitlab.com>
Approved-by: Max Woolf <mwoolf@gitlab.com>
Approved-by: Furkan Ayhan <furkanayhn@gmail.com>
Approved-by: Marcel Amirault <mamirault@gitlab.com>
Reviewed-by: Furkan Ayhan <furkanayhn@gmail.com>
Reviewed-by: Marcel Amirault <mamirault@gitlab.com>
Reviewed-by: Olena Horal-Koretska <ohoralkoretska@gitlab.com>
Reviewed-by: Alper Akgun <aakgun@gitlab.com>
Reviewed-by: Max Orefice <morefice@gitlab.com>
Reviewed-by: Max Woolf <mwoolf@gitlab.com>
Reviewed-by: Rajendra Kadam <rkadam@gitlab.com>
Co-authored-by: Rajendra Kadam <rkadam@gitlab.com>
Co-authored-by: Max Woolf <mwoolf@gitlab.com>