State Timeline: Support series names above the timeline bars

**Why is this needed**: There are numerous issues about state timeline alignment in the Grafana issues tracker and Grafana community forums. One common complaint is that the state timeline visualization cannot be made to line up with a timeseries visualization. A common dashboard configuration is to display a timeseries panel, with a state timeline directly below it, based on the same data and some threshold. See this example: https://community.grafana.com/t/align-timestamp-on-time-series-panel-with-state-timeline-on-a-dashboard/66767 **What would you like to be added**: An option to have the state timeline series name set *above* each series visualization as shown in that forum post, to support aligning timeseries panels and state timelines. **Who is this feature for?** Any user visualizing states and metrics associated with those states.