restyle to match dropshot, omicron, plus general style clean-up

[davepacheco]

This change does a one-time application of the following rustfmt changes:

normalize_comments = true
format_strings = true
wrap_comments = true
comment_width = 80

This is just to switch to C-style comments and rewrap strings and comments at 80 columns. I did these in separate commits so we could evaluate the options separately in case we don't like them. @andrewjstone what do you think?

We don't want to actually update rustfmt.toml for all the reasons discussed in oxidecomputer/dropshot#77.

If anybody has an outstanding change that they want to sync with this, I believe the thing to do is: immediately before sync'ing up with this change, commit any local changes, copy the above config lines (plus unstable_features = true) into your rustfmt.toml by hand, run cargo +nightly fmt to restyle your clone, remove the local changes to rustfmt.toml, commit the restyled version, and then sync up. I believe if you do this you will avoid conflicts from this change.

[andrewjstone]

This all looks good to me. Thanks @davepacheco.

If I understand correctly, we don't want to check in the rustfmt.toml changes because they rely on unstable which can change formatting on commit, right?

[davepacheco]

That is a big reason, yes. It was also rather a pain because you have to use nightly. New contributors have to set up their editor and it’s easy to forget the +nightly when you run by hand. If you forget to use nightly, it fails badly: just totally reformats things ignoring the unstable options.