Putting bootstrap host data into garage, and applying garage layout
diff, no longer happen simultaneously in the background. This was
causing some weird non-determinism in the startup which wasn't really
breaking anything, but made the logs harder to debug.
This also potentially fixes `waitForGarageAndNebula`, which was
neglecting to wait for nebula if there were allocations defined.
I had previously made the mistake of thinking that the Curve25519 key
which is generated for each host to use in nebula communication could
also be used for signing. This is not the case, Ed25519 is used for
signing and is different thant Curve25519.
Rather than figuring out how to convert the Curve25519 key into an
Ed25519 key, which there is no apparent support for in the standard
library, I opted to instead ship a separate key just for signing with
each host. Doing this required a bit of refactoring in order to keep all
the different keys straight and ensure all data which needs a signature
still has it.
This allows each host to verify the cert against the CA cert. We also
now have each host sign the yaml file that it posts to garage, to ensure
that a host can't arbitrarily overwrite another host's file.
