Continue the latency measurements while up/downloads are running

Having another speedtest that also measures latency and jitter is great! However, the way the test is currently setup, where it only runs the latency test before the download/upload tests are started, misses an important metric for connection performance: Bufferbloat, or excess latency under load (see https://en.wikipedia.org/wiki/Bufferbloat and https://www.bufferbloat.net/projects/bloat/wiki/Introduction/ for details, ).

So please consider extending the test to keep the latency measurements running during the throughput tests, and report the latency added relative to the baseline. See https://www.dslreports.com/speedtest/results/bufferbloat for the aggregate results of a speedtest that does this right.

The issue names no files or tests. Read the current speedtest flow to find where baseline latency is measured and where download/upload tests begin, then determine how measurements can continue during both throughput tests. Done means reporting latency added relative to the baseline, including jitter under load.

Written by the indexing model from the issue text.