PCI passthrough whitelisting & aliasing by device ID

Not all devices have a vendor_id and product_id. Not all hypervisors address devices in domain:slot:bus.func format. And it would be nice to be able to group devices at a granularity other than product/vendor ID for the purpose of identifying them in a flavor for attachment to a VM. This work aims to support identifying PCI devices in the [pci]passthrough_whitelist, the [pci]alias list, and the pci_passthrough_devices list (provided by the compute driver's get_available_resource) via an arbitrary device_id string. As a baseline, device_id strings will be matched exactly for purposes of whitelist filtering and claiming. As a stretch goal, a hook will be provided allowing the compute driver to perform matching in whatever way it deems appropriate.