* 1) Calculate pruning point incrementally
2) Add IsValidPruningPoint to pruning manager and consensus
3) Use reachability children for selected child iterator
* Add request IBD root hash flow
* Fix UpdatePruningPointByVirtual and IsValidPruningPoint
* Regenerate messages.pb.go
* Make the pruning point the earliest chain block with finality interval higher than the previous pruning point
* Fix merge errors
