bhyve: add more compliant NVMe Get/Set Features

Create a generic Get/Set Features by saving off the contents of CDW11
from the Set command and returning the saved value in the completion of
the Get command. Implementation allows providing optional implementation
for both Set and Get.

Add infrastructure to determine which feature ID's are namespace
specific and flag violations of this category of error.

Also adds the feature specific behavior of Set Features, Number of
Queues to only allow this command once per Controller reset.

Fixes UNH Tests 1.2, 5.4, and 5.5.6

Tested by: Jason Tubnor
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D24887