KVM: selftests: Make monitor_mwait require MONITOR/MWAIT feature

If this feature is not supported or is disabled by IA32_MISC_ENABLE on
the host, executing MONITOR or MWAIT instruction from the guest doesn't
cause monitor/mwait VM exits, but a #UD.

So, we need to skip this test if CPUID.01H:ECX[3] is cleared.

Signed-off-by: Zide Chen <zide.chen@intel.com>
Link: https://lore.kernel.org/r/20240411210237.34646-1-zide.chen@intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>