These were neither being returned or in many places reused.
Getting packets from a pool rather than deallocating and reallocating reduces memory churn which in turn reduces garbage collection time and frequency.
This allows different categories of stats to be shown, with options to list categories or show all stats.
Currently categories are scene and simulator and only a very few stats are currently registered via this mechanism.
This commit also adds percentage stats for packets and blocks reused from the packet pool.
Justin Clark-Casey (justincc)