feat(dashboards): add loki dashboards for gitalyctl

feat(dashboards): add loki dashboards for gitalyctl

What

Create two new panels for showing the count of logs over time.

Dashboard: https://dashboards.gitlab.net/dashboard/snapshot/RtLfrdOn6WZl5xOyy4jcl5DshjZRYrnt?orgId=1&from=now-7d&to=now

Why

We already have error rate in metrics, but we can also use the logs to see if there are any errror level logs.

Reference: https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/23969