Feature request: incremental statistics during a test run

[Packetslave]

It would be nice if ghz could output incremental statistics, e.g. "current QPS, current latency distributions, etc." every N seconds during a test run. Similar to what k6 does.

Use Case: start a long running load test, then run some expensive operations against the system to see how they affect the steady-state latency.

I'd even be happy if there was a mechanism to "subscribe" to incremental statistics when using the runner as a library, e.g. stream them to a channel or something.