fwget: Introduce new utility

This script's goal is to check the system for peripherals that needs
firmware and install the needed packages for them.
For now it only support pci subsystem and only video classes for AMD
and Intel GPUs.

Reviewed by: bapt
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D39825