Task #5844: COBALT PVSS: zero dynarrays pre-obs (while also logging obs ID,...

Task #5844: COBALT PVSS: zero dynarrays pre-obs (while also logging obs ID, data product names, etc). This is nice to have, because some events are written conditionally. If a subband has no dropped data, it's better to init that value to 0.0f. Some minor cleanups related to PVSS event logging is also included.