x86/vmx: introduce helper to set VMX_INTR_SHADOW_NMI

x86/vmx: introduce helper to set VMX_INTR_SHADOW_NMI

Introduce a small helper to OR VMX_INTR_SHADOW_NMI in
GUEST_INTERRUPTIBILITY_INFO in order to help dealing with the NMI
unblocked by IRET case.  Replace the existing usage in handling
EXIT_REASON_EXCEPTION_NMI and also add such handling to EPT violations
and page-modification log-full events.

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
master commit: d329b37d12132164c3894d0b6284be72576ef950
master date: 2022-12-19 11:23:34 +0100