LG1PCloudAmbStncl: Use RangeDescriptor obj instead of StagingBuffer

We directly use an instance of RangeDescriptor to avoid incurring
the memory cost of using a StagingBuffer here. It's unnecessary
since these stencils will always be 32bits large.

include/user/stencil.h

@@ -2,6 +2,7 @@
 #define _STENCIL_H
 
 #include <cstddef>
+#include <cstdint>
 #include <mentalEntity.h>
 
 namespace smo {
@@ -40,6 +41,8 @@ public:
 	 */
 	struct RangeDescriptor
 	{
+		uint32_t bodySpot;
+		size_t nContiguousSpots;
 	};
 
 	Stencil() = default;