Add USES=ansible for Ansible ports

The purpose of this new USES file is to provide a central place for
setting Ansible paths for modules and plugins. Perhaps in the future we
will extend to reduce boilerplate code in existing Ansible-related
ports.

PR: 255920
Reported by: lcook
Reviewed by: madpilot
Differential Revision: https://reviews.freebsd.org/D30312