Add PcloudAmbienceStencil, LG1PcloudAmbienceStencil

These two classes represent our first foray into stencil
construction. One of them standardizes PcloudAmbience stencils
across all stimbuffs, and the other specifies the internal
memory constraints and requirements for a LivoxGen1 device's
stencils.

stimBuffApis/livoxGen1/lg1PcloudAmbienceStencil.cpp

@@ -0,0 +1,19 @@
+#include "lg1PcloudAmbienceStencil.h"
+#include <unistd.h>
+
+namespace smo {
+namespace stim_buff {
+
+// Common IOEngineConstraints for LG1 ambience stencil StagingBuffer
+// (used for both input and output constraints)
+const StagingBuffer::IOEngineConstraints
+LG1PcloudAmbienceStencil::stencilBufferConstraints(
+	// slotStartAlignmentByteVal, slotPadToNBytes.
+	sizeof(void*),
+	sizeof(PcloudAmbienceStencil::RangeDescriptor),
+	// frameStartAlignmentByteVal, framePadToNBytes.
+	static_cast<size_t>(sysconf(_SC_PAGE_SIZE)),
+	static_cast<size_t>(sysconf(_SC_PAGE_SIZE)));
+
+} // namespace stim_buff
+} // namespace smo