CP-5643: Export the types of VGPUs

Signed-off-by: John Else <john.else@citrix.com>
CP-5643: Add relevant VGPU_types to the export table

Signed-off-by: John Else <john.else@citrix.com>
CP-5643: Import VGPU_type objects

Signed-off-by: John Else <john.else@citrix.com>
CP-5643: Fix DB filter

Signed-off-by: John Else <john.else@citrix.com>
CP-5848: Add vendor name to VGPU_type

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
Rename GPU_group.get_allowed_VGPU_types to get_enabled_VGPU_types

Signed-off-by: John Else <john.else@citrix.com>
Implement GPU_group.get_supported_VGPU_types

Refactor part of GPU_group.get_enabled_VGPU_types so it can be reused.

Signed-off-by: John Else <john.else@citrix.com>
Add GPU_group.supported_VGPU_types to the CLI

Signed-off-by: John Else <john.else@citrix.com>