Performance improvements

Major SHAMap reworking including eliminated mTNByID [RIPD-434]

Enlarge the tree node cache. This doesn't really increase memory usage (because most entries are pinned in the cache) but does reduce surging where entries are removed before they can be pinned if a lot of work is done in a small amount of time

Allow the RocksDB block size to be tuned and allow universal compaction to be selected