Switch from using bar gauges to tables for capacity planning in Grafana dashboards

Second iteration of our Capacity Planning report.

Capacity planning dashboards also link to graphs highlighting the historical values for the saturated metric.

Try it out here: https://dashboards.gitlab.net/d/general-triage/general-platform-triage?orgId=1

Click on the "Capacity Planning" row to expand it and see the report

Saturation Report

Linking to Resource Saturation Issues

Clicking on the "Find Issues" link will find issues related to the service and component that include the GitLab.com Resource Saturation label.

For example: https://gitlab.com/dashboard/issues?scope=all&utf8=%E2%9C%93&state=all&label_name[]=GitLab.com%20Resource%20Saturation

cc @marin @glopezfernandez