Network sync refactoring (part 6) (#11940)

* Extract `NetworkKVProvider` trait in `sc-authority-discovery` and remove unnecessary dependency

* Extract `NetworkSyncForkRequest` trait in `sc-finality-grandpa`

* Relax requirements on `SyncOracle` trait, remove extra native methods from `NetworkService` that are already provided by trait impls

* Move `NetworkSigner` trait from `sc-authority-discovery` into `sc-network-common` and de-duplicate methods on `NetworkService`

* Move `NetworkKVProvider` trait from `sc-authority-discovery` into `sc-network-common` and de-duplicate methods on `NetworkService`

* Minimize `sc-authority-discovery` dependency on `sc-network`

* Move `NetworkSyncForkRequest` trait from `sc-finality-grandpa` to `sc-network-common` and de-duplicate methods in `NetworkService`

* Extract `NetworkStatusProvider` trait and de-duplicate methods on `NetworkService`

* Extract `NetworkPeers` trait and de-duplicate methods on `NetworkService`

* Extract `NetworkEventStream` trait and de-duplicate methods on `NetworkService`

* Move more methods from `NetworkService` into `NetworkPeers` trait

* Move `NetworkStateInfo` trait into `sc-network-common`

* Extract `NetworkNotification` trait and de-duplicate methods on `NetworkService`

* Extract `NetworkRequest` trait and de-duplicate methods on `NetworkService`

* Remove `NetworkService::local_peer_id()`, it is already provided by `NetworkStateInfo` impl

* Extract `NetworkTransaction` trait and de-duplicate methods on `NetworkService`

* Extract `NetworkBlock` trait and de-duplicate methods on `NetworkService`

* Remove dependencies on `NetworkService` from most of the methods of `sc-service`

* Address simple review comments