core: refactor block queue

It requires only two methods from Blockchainer: AddBlock and
BlockHeight. New interface will allow to easily reuse the block queue
for state exchange purposes.

pkg/core/blockchainer/blockchainer.go

@@ -22,7 +22,7 @@ type Blockchainer interface {
 	ApplyPolicyToTxSet([]*transaction.Transaction) []*transaction.Transaction
 	GetConfig() config.ProtocolConfiguration
 	AddHeaders(...*block.Header) error
-	AddBlock(*block.Block) error
+	Blockqueuer // Blockqueuer interface
 	CalculateClaimable(h util.Uint160, endHeight uint32) (*big.Int, error)
 	Close()
 	InitVerificationVM(v *vm.VM, getContract func(util.Uint160) (*state.Contract, error), hash util.Uint160, witness *transaction.Witness) error

pkg/core/blockchainer/blockqueuer.go

@@ -0,0 +1,9 @@
+package blockchainer
+
+import "github.com/nspcc-dev/neo-go/pkg/core/block"
+
+// Blockqueuer is an interface for blockqueue.
+type Blockqueuer interface {
+	AddBlock(block *block.Block) error
+	BlockHeight() uint32
+}

pkg/network/blockqueue.go

@@ -11,7 +11,7 @@ type blockQueue struct {
 	log         *zap.Logger
 	queue       *queue.PriorityQueue
 	checkBlocks chan struct{}
-	chain       blockchainer.Blockchainer
+	chain       blockchainer.Blockqueuer
 	relayF      func(*block.Block)
 }
 
@@ -21,7 +21,7 @@ const (
 	blockCacheSize = 2000
 )
 
-func newBlockQueue(capacity int, bc blockchainer.Blockchainer, log *zap.Logger, relayer func(*block.Block)) *blockQueue {
+func newBlockQueue(capacity int, bc blockchainer.Blockqueuer, log *zap.Logger, relayer func(*block.Block)) *blockQueue {
 	if log == nil {
 		return nil
 	}