message: Add missing atomic_fence intrinsics as nops
  Fixes
diff: @@ -88,7 +88,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  this.write_scalar(val, place.into())?;
  }
  - "atomic_fence_acq" => {
  + "atomic_fence_acq" |
  + "atomic_fence_rel" |
  + "atomic_fence_acqrel" |
  + "atomic_fence" => {
  // we are inherently singlethreaded and singlecored, this is a nop
  }
  