(CAT-372) - add var support to vagrant provisioner

[jordanbreen28]

Summary

To use multi-node provisioning locally with vagrant we need to be able to
assign arbitrary tags to the nodes we deploy.
Other provisioners do this with a parameter called vars.

This PR introduces support for this, and essentially copies what is
already present in the other bolt tasks in this module.

Additional Context

Litmus

bundle exec rake 'litmus:provision[vagrant, generic/debian10, role: worker1]'

Bolt

bundle exec bolt task run provision::vagrant --targets localhost  action=provision platform=generic/debian10 vars='role: worker1'

Will return an inventory file like

  - uri: 127.0.0.1:2200
    config:
      transport: ssh
      ssh:
        user: vagrant
        host: 127.0.0.1
        host-key-check: false
        port: 2200
        run-as: root
        connect-timeout: 120
        private-key: "path/vagrant.key.ed25519"
    facts:
      provisioner: vagrant
      platform: generic/debian10
      id: 57169c9e3f884f0dbe94dc26cdd8b7f0
      vagrant_env: "path/.vagrant/generic-debian10-6"
    vars:
      role: worker1

Related Issues (if any)

Mention any related issues or pull requests.

Checklist

• 🟢 Spec tests.
• 🟢 Acceptance tests.
• Manually verified.

[LukasAud]

LGTM