livoxGen1: Implement StimBuff add/del from StimProducers

There seems to be a bug where two or more stimProducers
or stimBuffs get initialized at once but we can deal with that
tomorrow.

stimBuffApis/livoxGen1/pcloudStimulusProducer.h

@@ -62,6 +62,11 @@ public:
 	void start() override;
 	void stop() override;
 
+	std::shared_ptr<StimulusBuffer> getOrCreateAttachedStimulusBuffer(
+		const std::shared_ptr<device::DeviceAttachmentSpec>
+			&deviceAttachmentSpec,
+		int histbuffMs) override;
+
 protected:
 	void stimFrameProductionTimesliceInd() override;