feat: add ansible run to the deploy command

[jacderida]

• 8cede34 feat: add ansible run to the deploy command

  Right now this only provisions the genesis node. We need to implement the retrieval of the genesis
  IP and peer ID before we can run against the remaining nodes.

  It uses a very similar pattern to Terraform, with an interface, so that we can do behaviour-based
  unit testing.

• 7d86f8b tests: reorganise unit tests

  There were over 700 lines of tests and setup code inside a single test module, which was becoming
  unwieldy to work were.

  This splits the setup code into one module, then a module for each function on TestnetDeploy that
  is under test. With the use of modules, the function name was removed from the test case names.

• 8741d35 refactor: split deploy into smaller functions

  The smaller functions are easier to test and don't require as much mocking setup.

• f9ff92c feat: run ansible against remaining nodes

  The multiaddr of the genesis node is composed by running ansible-inventory to get its IP address,
  by running the rpc client to get its peer ID.

  After we have that, we can then run against the remaining nodes.

  Those two functions were separated for easier test setup and admin.

• 81dd653 feat: ssh availability check

  It's possible that before we run Ansible, the SSH service is not yet running on the genesis node.
  This is something we seen happen occasionally, so we added in a little loop to sit and wait for it
  to become available.

  We only check this for the genesis run because the remaining nodes are provisioned after genesis, by
  which point the SSH service should be available.

• f2fe39e feat: provide --node-count arg for deploy cmd

  This will control how many node processes run on each VM. The default is 20.

• 18b26be feat: run deploy with custom binary

  If the --branch and --repo-owner arguments are used, the build machine will be spun up to build
  a custom binary, which will then be uploaded to S3. Then when the nodes are being provisioned, this
  binary will be pulled in.

• ce8129d feat: provide setup command

  This creates the .env file by gathering input from the user, trying to assist them with which
  values should be provided.

  We are leaving it to the user to setup Terraform and Ansible on their OS.

• 36106c5 docs: provide setup and usage instructions

  This still needs to be extended with some information on how to obtain the IP addresses of each
  VM.

• 58ce76d feat: provide inventory command

  This will produce a list of all the VMs participating in the testnet, along with the SSH user for
  the cloud provider.

• a31ee5b chore: respond to feedback

  Addresses two issues that were noted during review:

  • Provide more helpful error message when inventory list is empty
  • Set other environment variables for Digital Ocean based on the DO_PAT variable

  For the first issue, there are a few different ways in which it might be possible for the
  environment to be non-existent. These were documented with comments in the code, which you can see
  in the diff.