Use ChefAPI gem for deleting the node/client instead of shelling out to `knife`

### :construction:  Not ready yet  :construction: 

As reported in #2476, shelling out to `knife` can be problematic as Vagrant modifies `GEM_PATH` and other environment.

This PR borrows ideas from the [vagrant-butcher](https://github.com/cassianoleal/vagrant-butcher) plugin, but uses the [ChefAPI gem](https://github.com/sethvargo/chef-api) to communicate with the Chef server.

**Note**: At least tests and proxy and SSL configurations are still missing, but otherwise this should be working. I opened the PR to get feedback. /cc @sethvargo @cassianoleal

Fixes #2476