feat: Gitaly Stable Counterpart report for issues

What

Create a new report for Gitaly Stable Counterpart to show a stacked bar chart by the the ~work::* label.

Why

At the moment there is no clear indicator that the Gitaly service has a large amount of operations work vs project work, SRE should always aim to have 50% split between operations work and project work. One of the goals of stable counterparts is to improve the operations of a specific service.

Reference: https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/16924