[reconfigurator-cli] Customize log outputs

[jgallagher]

My main goal with this PR was to fix the failing test on #7307 by emitting slog logs without timestamps (to avoid having to redact them in expectorate tests, and because they're not actually useful in a CLI). As a nice side effect, the output in a terminal is much nicer.

On main, I see this when planning a blueprint:

I assume this is some bad interaction between slog-async / logs going to stderr / reedline.

On this branch, I now get:

[andrewjstone]

This looks so much better! Thanks @jgallagher

[davepacheco]

Thank you for doing this! I'm sorry to have left this particular piece of debt.

[sunshowers]

Thanks for doing this :)

It would be great to publish a good logger for CLI tools at some point. I'm partial to the general format Rust and Cargo use:

trace: ...
debug: ...
info: xyz
warn: something strange
error: whoops

where trace/debug/info are in bold, warn is in bold yellow, and error is in bold red. This is great though!

[davepacheco]

This is getting a bit far afield for this issue but: I've long been meaning to pull the logging config stuff that most of Omicron uses (e.g., https://docs.rs/dropshot/latest/dropshot/enum.ConfigLogging.html) out of dropshot. ConfigLogging could grow a new variant for CLI tools (or we could maybe change what StderrTerminal does) and then a lot of our stuff might pick up the new behavior with minimal changes. I'm not attached to this. I just want there to be a low-boilerplate way to do the thing that we want our stuff to do (and that's what ConfigLogging was intended to be).