Allow compilation with nvcc 11.4 (#7131)

* Use type aliases for discard iterators

* update to include host_vector as thrust 1.12 doesn't bring it in as a side-effect

* cub::DispatchRadixSort requires signed offset types

src/predictor/gpu_predictor.cu

@@ -5,6 +5,7 @@
 #include <thrust/device_ptr.h>
 #include <thrust/device_vector.h>
 #include <thrust/fill.h>
+#include <thrust/host_vector.h>
 #include <GPUTreeShap/gpu_treeshap.h>
 #include <memory>