As we moved most of the creation of a BufferPool to be via the
Streaming::pool() method, which uses a thread-local, it makes sense
to start cleaning up the design and make it more modern C++.
The above mentioned method would return a reference and you'd see
loads of places use `auto &pool =` which is less than ideal.
As the number of places where we actually instantiate a BufferPool
goes down, the usage of some sort of smart pointer makes more sense.
This now makes all APIs use BufferPool be wrapped in a shared_ptr.
Replace the m_buckets unsorted map with a lock-free version
based on atomic pointers. (BucketMap)
remove the m_leafs and move those into the bucket struct.
Make the access to the jumptable transactional to avoid one big lock
over all datastructures.
On my threadripper 2990WX the entire 150GB BCH blockchain was
parsed and imported in under 3 hours.
tomFlowee
TomZ