StimBuff: Use a single StagingBuffer for all StimFrames

We now allocate all the stimFrames for a StimBuffer using a
single StagingBuffer. This gives us all the benefits we're
looking for (pinning, alignment, etc).

stimBuffApis/livoxGen1/pcloudStimulusProducer.h

@@ -86,6 +86,7 @@ public:
 	StagingBuffer assemblyBuffer;
 	IoUringAssemblyEngine ioUringAssemblyEngine;
 	StagingBuffer collationBuffer;
+	size_t tempStimulusFrameMem;
 	StimulusFrame tempStimulusFrame;
 	std::shared_ptr<MeshStimulusBuffer> meshStimulusBuffer;
 	std::shared_ptr<PcloudIntensityStimulusBuffer> intensityStimulusBuffer;