Move `NextFoundInstanceOf`, `NextInstanceOf` and `Metrics` helpers

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/136905



Merged-by: Rémy Coutable <remy@rymai.me>
Approved-by: Rémy Coutable <remy@rymai.me>
Approved-by: Chad Woolley <cwoolley@gitlab.com>
Reviewed-by: Kamil Trzciński <ayufan@ayufan.eu>
Reviewed-by: Rémy Coutable <remy@rymai.me>
Reviewed-by: Hunar Khanna <hkhanna@gitlab.com>
Co-authored-by: Kamil Trzciński <ayufan@ayufan.eu>