The original idea behind this change was to remove a use of the
deprecated CancelRequest method. Simply removing it would've been an
option, but I couldn't resist and did a bit of a refactoring instead.
All remote sealing code was contained in a single giant function. Remote
sealing is now extracted into its own object, remoteSealer.
* miner: commit state which is relative with sealing result
* consensus, core, miner, mobile: introduce sealHash interface
* miner: evict pending task with threshold
* miner: go fmt