consensus: handle justification sync for blocks authored locally (#8698)

* consensus: add trait to control justification sync process

* network: implement JustificationSyncLink for NetworkService

* slots: handle justification sync in slot worker

* babe: fix slot worker instantiation

* aura: fix slot worker instantiation

* pow: handle justification sync in miner

* babe: fix tests

* aura: fix tests

* node: fix compilation

* node-template: fix compilation

* consensus: rename justification sync link parameter

* aura: fix test compilation

* consensus: slots: move JustificationSyncLink out of on_slot