Worker controls to turn on/off console messages

[michaelfig]

Now that console handling will be implemented consistently in the supervisor, even when running on-chain, we should consider providing means to enable and disable the routing of those messages from the worker to its own stderr or the kernel.

This is likely part of a larger plan for deciding where messages are routed.

With #4814 to track the review/rewrite, I'm ok with removing consensusMode. Please make some tickets (if you haven't already) for building the alternate controls we talked about today ("start/stop sending console messages to the kernel process", and maybe "start/stop sending console messages to your own local stdout/stderr"). I think those are lower priority but let's not forget what our plan was.

Originally posted by @warner in #4768 (review)