I don't think that printing low-level I/O and frames is beneficial to
testing command-level functionality. Protocol-level testing, yes. But
command-level functionality shouldn't care about low-level details in
most cases. This output makes tests more verbose and harder to read.
It also makes them harder to maintain, as you need to glob over various
dynamic width fields.
Let's remove these low-level details from many of the wireprotov2
tests.