KVM: selftests: Add an x86-only test to verify nested exception queueing

KVM: selftests: Add an x86-only test to verify nested exception queueing

Add a test to verify that KVM_{G,S}ET_EVENTS play nice with pending vs.
injected exceptions when an exception is being queued for L2, and that
KVM correctly handles L1's exception intercept wants.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-27-seanjc@google.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>