feat: provide node-manager command

[jacderida]

• 58aa96f refactor: download and extract using sn-releases crate

  The code for downloading and extracting release binaries from Github and S3 was being repeated in
  several different places, so we decided to put some common code for it in a crate.

  We are now updating safeup to use it, which removes both the github and s3 modules, and makes
  the install_bin tests simpler.

  From the user's point of view, functionally everything should be the same.

  I also added a quick Vagrantfile here that can be used for testing safeup. This is useful if you
  don't want your local machine littered with binaries that were only used for testing.

• 3d2b33a feat: provide node-manager command

  BREAKING CHANGE: the new settings file will have additional entries for keeping track of the
  safenode-manager installation. Previously serialised settings files will be incompatible with this
  change. Users will need to clear their previous settings file when they upgrade.

  This will install the node manager alongside the other binaries. After the sn-releases crate was
  extended for the new release type, adding the new command was quite straight forward, since it's
  just the installation of another binary.

  At some point later we may need to extend this installation to also distribute the RPC client, which
  may be required for the node manager if we're going to use it in service shutdown commands. For now
  though, it's just distributing the safenode-manager binary.