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.
The new code makes it a lot clearer what the sources of each
file/directory is, and makes it more difficult to forget to add a file
or directory. This will be helpful when it comes to bootstrapping an
entire network, which will require yet a third way of generating
bootstrap files.
