CA-122441: Update group supported/enabled types after GCing PGPUs

Signed-off-by: John Else <john.else@citrix.com>
Log every time we GC a PGPU

Signed-off-by: John Else <john.else@citrix.com>
Add new fields to make_vgpu_type

Signed-off-by: John Else <john.else@citrix.com>
Improve consistency of test_common.ml

Fix all the make_* functions such that they return the ref of the thing
which they created.

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

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