This is a subtask of
IMPALA-3200. The first milestone we want to hit is a usable buffer pool that does not support spilling. This would include the actual buffer pool, minus the logic for flushing unpinned blocks to disk (if it runs out of buffers, we can just terminate queries).
Initially we should just allocate memory from TCMalloc.
It would also include the initial work to port over exec nodes to the new buffer pool: enough to run some queries using them.