(PUP-8015) Add a puppet ssl face for generating csrs without needing to connect to a master

[barriserloth]

This commit moves the puppet-agent-bootstrap code created by Adrien
Thebo (https://github.com/adrienthebo/puppet-agent-bootstrap/) to the
puppetlabs github space, and adds rspec tests to go along with the
bootstrap changes.

[puppetcla]

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[puppetcla]

CLA signed by all contributors.

[puppetcla]

CLA signed by all contributors.

[joshcooper]

Note, I'd like to reserve the ssl subcommand for future work around fixing/consolidating the broken certificate* subcommands, and adding this type of functionality to it as well.

[ajroetker]

@joshcooper do you have another suggestion for the subcommand name?

[joshcooper]

We released puppet ssl in puppet6, which should supersede the need for this application. If anything is missing, please file a PUP ticket and resubmit a PR based on the latest puppet#master branch.