KVM: selftests: Print out failing MSR and value in vcpu_set_msr()

KVM: selftests: Print out failing MSR and value in vcpu_set_msr()

Reimplement vcpu_set_msr() as a macro and pretty print the failing MSR
(when possible) and the value if KVM_SET_MSRS fails instead of using the
using the standard KVM_IOCTL_ERROR().  KVM_SET_MSRS is somewhat odd in
that it returns the index of the last successful write, i.e. will be
'0' on failure barring an entirely different KVM bug.  And for writing
MSRs, the MSR being written and the value being written are almost always
relevant to the failure, i.e. just saying "failed!" doesn't help debug.

Place the string goo in a separate macro in anticipation of using it to
further expand MSR testing.

Link: https://lore.kernel.org/r/20230311004618.920745-12-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>