Add Honeycomb tracing to all Boulder components which act as
HTTP servers, gRPC servers, or gRPC clients. Add many values
which we currently emit to logs to the trace spans. Add a way to
configure the Honeycomb integration to our config files, and by
default configure all of our tests to "mute" (send nothing).
Followup changes will refine the configuration, attempt to reduce
the new dependency load, and introduce better sampling.
Part of https://github.com/letsencrypt/dev-misc-tickets/issues/218