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).
* PcloudStimulusProducer now has member sh_ptr<StimulusBuffer>s.
* StimulusProducer now has a vector<sh_ptr<StimulusBuffer>s.
Created new stimbuff-type-specific
Pcloud[Xyz|I|Ambience]StimulusBuffer classes for representing each
stim feature exposed by livoxGen1's PcloudStimulusProducer.