Host types have been moved within the `bootstrap` package.
Refactored how boostrap FS is interacted with. There is now a
`Bootstrap` struct which has pre-loaded all data within the bootstrap
FS. This helps centralize the logic around reading the data (though not
yet completely).
Choosing of the garage node to interact with no longer occurs in like
three different places. It occurs at the environment level now, and is
aided by the new `garage.Peer` type.
