Lg1: Implement both light|darkAmbience stimBuffs & their production

We now produce both light and dark ambience stimframes into
stimbuffs for the LivoxGen1 lidar devices.

stimBuffApis/livoxGen1/meshStimulusBuffer.h

@@ -15,8 +15,8 @@ class StimulusProducer;
 /**
  * MeshStimulusBuffer is a specialized StimulusBuffer for mesh data.
  * Intrinsic threshold params are not allowed on mesh qualeIfaceApi lines;
- * attach postrin(...) / negtrin(...) specifiers to a pcloudAmbience nontrin
- * spec instead.
+ * attach postrin(...) specifiers to a pcloudDarkAmbience line or
+ * negtrin(...) specifiers to a pcloudLightAmbience line instead.
  */
 class MeshStimulusBuffer
 :	public StimulusBuffer