Add support for vm.remove-device for pci hotunplug

[bryteise]

@sboeuf where can I find information on the schemas request body? I am guessing this API endpoint lets one remove any of the devices added via the add-{device,fs,pmem,net,vsock} but I am not sure.

[sboeuf]

Any device that has been added can be removed based on its id. So the schema request body simply expect {id: 12} if 12 is the id from the device you want to remove.