qemu: add cpu_features option

[ port from runtime commit 0100af18a2afdd6dfcc95129ec6237ba4915b3e5 ]

To control whether guest can enable/disable some CPU features. E.g. pmu=off,
vmx=off. As discussed in the thread [1], the best approach is to let users
specify them. How about adding a new option in the configuration file.

Currently this patch only supports this option in qemu,no other vmm.

[1] https://github.com/kata-containers/runtime/pull/2559#issuecomment-603998256

Signed-off-by: Jia He <justin.he@arm.com>
Signed-off-by: Peng Tao <bergwolf@hyper.sh>

src/runtime/virtcontainers/persist/api/config.go

@@ -54,6 +54,9 @@ type HypervisorConfig struct {
 	// MachineAccelerators are machine specific accelerators
 	MachineAccelerators string
 
+	// CPUFeatures are cpu specific features
+	CPUFeatures string
+
 	// HypervisorPath is the hypervisor executable host path.
 	HypervisorPath string