Certs module cleanup

* Use custom providers for certs generation instead of exec katello-ssl-tool
* Move the certs bits from other modules: every service has dedicated pp file with all things specific the the service
* Httpd doesn't use candlepin-ca as ssl cert, instead ca generates new ssl cert to be used. Thanks to chaining, the verification from clients should still work without issues (the approach already tested previously with nodes)
* Foreman uses certs originate in candlepin-ca instead of puppetca certs (as it already did with nodes)