puppet_agent : Add task and plan for running Puppet agent

When Bolt runs a command on a target it marks the result as a failure if the command returns a non-zero exit code. This causes issues when a user starts a Puppet agent run with Bolt, as the agent may run successfully but return a non-zero exit code.

The puppet_agent module should include a task for running the Puppet agent on a list of targets, as well as a plan that will check if the targets have the agent installed and start a run on the targets that do.

This work is part of a Bolt ticket: https://github.com/puppetlabs/bolt/issues/2022