Added mining for POS (#3187)

* added comunication with channels

* added final mining

* removed trash

* bug fixing

* async calls

* one thread

* tests

* better comments

* no lock

* better placing of skipCycleHack

* removed long timer

* moved transitioned block processing

* better naming

* disabled updates on blocks

* sync.Cond

* 2 sync.Cond

* better locking

* Use single sync.Cond. Proposer shutdown

Co-authored-by: yperbasis <andrey.ashikhmin@gmail.com>