GPU Metal: commit the memory clear through CommitStream

The GPUMemClean16 blit committed its command buffer directly, so the
stream kept the committed buffer as its open one, and the next encoder on
that stream aborted with "failed assertion _status <
MTLCommandBufferStatusCommitted". The clear was also never waited for.

Author: ktf

GPU/GPUTracking/Base/metal/GPUReconstructionMetalKernelsSpecialize.inc

@@ -23,5 +23,5 @@ inline void GPUReconstructionMetal::runKernelBackend<GPUMemClean16, 0>(const krn
   [blit fillBuffer:mInternals->mem_gpu range:NSMakeRange(offset, length) value:0];
   [blit endEncoding];
 
-  [cb commit];
+  CommitStream(_xyz.x.stream);
 }