Revert "fix levelup read-stream-test: run callback from next in next tick"

This reverts commit 6ec8767b06170090b8ecfdf49b515f9b6f0b4d27.
inherit from abstract-leveldown
inherit from AbstractLevelDOWN & AbstractIterator
remove some c++
use abstract-leveldown for ChainedBatch
remove unused macro
remove some c++ from batch