hp malloc: fix shm statistics

	* processes now update fragment statistics for each bucket
	* the MI workers iterate and aggregate all memory information
	* the built-in maximum sampling rate is 200ms
		- repeating a fetch in < 200ms will return the same results
	* this patch also corrects a rare deadlock in hp_realloc
		- hp_realloc "growth" may deadlock with hp_malloc "shrink"
		- the best solution is to drop the "growth" realloc operation
		- this also merges well with the allocator fragmentation requirements