Add optional Grafana annotations for test start/end
Internally, GitLab uses Grafana for visualizing the metrics of our performance environments. When we are analyzing performance data, the current strategy for answering "What test caused this?" is to correlate the API endpoint traffic graph with other metrics to determine when certain tests started/ended.
It would be convenient to instead have the option to configure a Grafana URL + token at run start, and if that configuration is present, use the Grafana annotations API to create Annotations for these events that we can then overlay on other charts when we need it.