[BP 7.2.4] - Ensure swapper will not spin continously if jemalloc resident mem > RSS

When under swap, jemalloc malloc heap size can be higher than RSS where jemalloc heap stats include memory that have been swapped out by OS. Instead of using jemalloc heap in controlling eviction, use plasma stats with estimation of jemalloc fragmentation, where Jemalloc fragmentation is estimated periodically based on heap usage. If system is under swap, plasma will use a pre-determined jemalloc fragmentation instead of calculating based on heap usage, since heap stats will not be accurate at that time.