Lg1: Implement both light|darkAmbience stimBuffs & their production

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

include/user/deviceAttachmentSpec.h

@@ -13,7 +13,7 @@ namespace smo {
 namespace device {
 
 /* Carrier used by the DAP spec parser to pass one parenthesized segment
- * (e.g. postrin(interest-pc=85) or pcloudAmbience(...)) up the reduction
+ * (e.g. postrin(interest-pc=85) or pcloudLightAmbience(...)) up the reduction
  * stack; the spec_body reduction classifies segments and populates the
  * DeviceAttachmentSpec. Defined here so both the parser header and consumers
  * of the generated header see the type.