StagingBuff: support both Mlock & IOUring pin; Use in IoUAssmEngn

We use io_uring_register_buffers() for IoUringAssemblyEngine instead
of using mlock(). This __appears__ to have reduced CPU utilization on
the Dell laptop. Could also be that we recently upgraded total RAM
from 8GiB to 32GiB.

stimBuffApis/livoxGen1/pcloudStimulusProducer.h

@@ -52,11 +52,11 @@ public:
 
 	~PcloudStimulusProducer() = default;
 
-	// Non-copyable, movable
+	// Non-copyable, non-movable: pinners hold buffer instance references
 	PcloudStimulusProducer(const PcloudStimulusProducer&) = delete;
 	PcloudStimulusProducer& operator=(const PcloudStimulusProducer&) = delete;
-	PcloudStimulusProducer(PcloudStimulusProducer&&) = default;
-	PcloudStimulusProducer& operator=(PcloudStimulusProducer&&) = default;
+	PcloudStimulusProducer(PcloudStimulusProducer&&) = delete;
+	PcloudStimulusProducer& operator=(PcloudStimulusProducer&&) = delete;
 
 	// Control methods
 	void start() override;
@@ -94,7 +94,10 @@ public:
 	StagingBuffer assemblyBuffer;
 	IoUringAssemblyEngine ioUringAssemblyEngine;
 	StagingBuffer collationBuffer;
+	std::unique_ptr<StagingBuffer::MlockPinner> collationBufferMlockPinner;
 	StagingBuffer averageIntensityBuffer;
+	std::unique_ptr<StagingBuffer::MlockPinner>
+		averageIntensityBufferMlockPinner;
 	size_t tempStimulusFrameMem;
 	StimulusFrame tempStimulusFrame;
 	std::atomic<std::shared_ptr<MeshStimulusBuffer>> meshStimulusBuffer;