[EE] Add backtrace to Gitaly performance bar
This adds the backtrace to a table to show exactly where the Gitaly call was made to make it easier to understand where the call originated.
This change also collapses the details in the same row to improve the usability when there is a backtrace.
CE port: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/27345
Edited by Stan Hu