[CHEF-18897] Add the berkshelf gem and use the chef-cli from the Chef-DKE

[ashiqueps]

Description

In chef-test-kitchen-enterprise, we have a dependency on the berkshelf and chef-cli. The berkshlf is a gem dependency so I added that in the gemspec file. The chef-cli is a binary dependency, so it expects the chef/chef-cli or chef/chef-development-kit-enterprise hab package to be installed already or it will show an error to install the same.

Related Issue

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (non-breaking change that does not add functionality or fix an issue)

Checklist:

• I have read the CONTRIBUTING document.
• I have run the pre-merge tests locally and they pass.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• If Gemfile.lock has changed, I have used --conservative to do it and included the full output in the Description above.
• All new and existing tests passed.
• All commits have been signed-off for the Developer Certificate of Origin.