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.

include/user/stimulusProducer.h

@@ -72,6 +72,10 @@ public:
 	std::shared_ptr<StimulusBuffer> getAttachedStimulusBuffer(
 		const std::shared_ptr<device::DeviceAttachmentSpec>& spec) const;
 
+	virtual std::shared_ptr<StimulusBuffer> getOrCreateAttachedStimulusBuffer(
+		const std::shared_ptr<device::DeviceAttachmentSpec>& deviceAttachmentSpec,
+		int histbuffMs) = 0;
+
 protected:
 	SpinLock frameAssemblyRateLimiter;