CP-5597: Add VGPU_type functionality

VGPU_type objects are added to the database when a new vGPU-capable PGPU is added to the host. A group now keeps a field of supported and allowed VGPU_types which is queried when VGPUs are created.

This required rewriting the way we scrape PCI information from the `pci.ids` database. This has resulted in a new module, `Pci_db` which is a generic parser of this database which can be queried. The old method for getting information (the `pci-info` python script) and its uses have been removed.