ANDROID: pkvm: vmx: Handle nmi window vmexit

The nmi window vmexit is handled by the pkvm hypervisor to clear
CPU_BASED_NMI_WINDOW_EXITING. Then return back to the host KVM to make
the request KVM_REQ_EVENT to inject any pending nmi.

Bug: 391539939
Test: pKVM works
Upstream-Task: 402758258

Change-Id: I8f622134563eadfd32cffec83f380de7029ace0f
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Signed-off-by: Dmytro Maluka <dmaluka@google.com>