cvm guest vsm: implement get register for vsmpartitionstatus and vsmvpstatus

[sluck-msft]

VsmPartitionStatus and VsmVpStatus should be available for guests to try to read.

[smalis-msft]

We should also be advertising the HV_PARTITION_PRIVILEGE_ACCESS_VP_REGISTERS privilege. Windows apparently never checks for this, but we should be spec compliant.