Clean up and remove stale code

[andrewjstone]

Clean up the bootstrap agent in preparation for multirack support. This
ended up requiring a few other significant changes in other crates.

As a first step, we should recognize that the bootstrap agent dropshot
API is never going to support TLS. This is why we have sprockets
running over the bootstrap network in the first place. All cross sled
interactions should use sprockets for security. However, we need to
bootstrap the system and so we allow wicketd to talk to the local
bootstrap agent on it's own sled. This occurs over the lockstep API.
With some further changes, we were able to remove the bootstrap agent
API altogether. Additionally, some sprockets related names were changed
to enhance clarity.

For historical reasons, we used Baseboard throughout wicket, but with
the changes made to remove the bootstrap agent dropshot API, we only
have access to BaseboardIds, as that's what the majority of the system
works with. Therefore, we migrated many uses of Baseboard to use
BaseboardId instead. This is a much more straightforward type to use.

As part of the change to using BaseboardIds in wicketd, we wanted to
remove optionality for it. The switch zone should always know its own
Baseboard through the injected file, and so now we fail immediately if
the file does not exist.

In order to get a non-optional BaseboardId we wanted to make
conversion from Baseboard to BaseboardId infallible. I had started
doing this by removing the Unknown variant from Baseboard and
reworking all users. When I had finished I had discovered that this
changes a few APIs in a non-backwards compatible manner. As this PR is
already very large, I didn't want to make that change. So I went back
and re-added the Unknown variant, panicking if it ever gets used.
I will clean this up in a follow up that also removes the bootstore
which is a primary user. The bootstore itself cannot ever have an
Unknown variant in production, so this is fine for now.

To fix a chicken and egg problem where the now gone bootstrap agent
api was needed for wicketd to learn its bootstrap-agent-lockstep-api
address, we now plumb that address through SMF directly, since the
bootstrap agent already knows it when creating the switch zone.

Since rack reset doesn't actually work, I also went ahead and removed
all the related code. This simplifies things immensely. We can add back
working reset functionality in the future, that will work a lot more
like the clean slate script.

There was also an old, unused UpdateManager, that was only called from
an unused bootstrap agent API. That has also been removed.

[andrewjstone]

This needs to be tested on a racklette and on a4x2.