harness: consume output of balancer when running tests

[dyc3]

When running harness tests against the balancer, the balancer outputs a ton of logs. It would be nice if the harness could consume these logs and re emit them so that they don't show up in the output unless --nocapture is used. Note that --nocapture already exists and so implementing that part is not necessary, eg. cargo test -- --nocapture

[Victor-M-Giraldo]

I would like to work on this.

[Victor-M-Giraldo]

The log crate seems to do this. If you don't want to add another crate, could you remind me of what the method for the likely fix for this issue is?

I believe it was reading in the standard output and immediately printing it back out, but I didn't get to write it all down.

[dyc3]

We are already using the tracing crate for logging.

You need to grab the standard out and standard error of the child process, and immediately log it back out as the parent process.