add a powerboard temperature monitoring graph in GUI

This MR adds a powerboard temperature monitoring graph at the testing page.

To avoid conflicts etc., lease merge those MRs first: berkeleylab/labremote-apps/powertools!136 (merged), !73 (merged), !71 (merged)

The added part look like this:

With start and stop monitoring button, and clear monitor data button. Users can select which powerboard to monitor at the top of the page where the powerboard selection part is. Users can select what temperature data to show on the graph. Users can also select to save the monitor data to a csv. With proper configuration in config file, monitor data will also be pushed to grafana (see berkeleylab/labremote-apps/powertools!136 (merged)).