Enable users to choose single or multi-connection test

[sir-bogbrush]

Description

It would be useful if the user interface allowed a user to choose whether to have a single or multi-connection test themselves.

• Single connection: good indicator of expected performance for a single TCP session. This reflects how applications really perform.
• Multi connection: good indicator of overall available bandwidth between client and server

Why it should be implemented

We use Librespeed on our WAN so that we can support users without worrying about iperf etc. Sometimes a single-connection test is more useful because it provides an indicator of throughput to expect from most applications for a given latency.

Optional: screenshots

Speedtest.net have a good example, it is just a toggle switch visible to all users