KVM: selftests: Print out guest RIP on unhandled exception

Use the newfanged printf-based guest assert framework to spit out the
guest RIP when an unhandled exception is detected, which makes debugging
such failures *much* easier.

Link: https://lore.kernel.org/r/20230729003643.1053367-34-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>