[#86] Add alphabet contract processor

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/innerring/processors/alphabet/process_emit.go

@@ -0,0 +1,23 @@
+package alphabet
+
+import (
+	"github.com/nspcc-dev/neofs-node/pkg/innerring/invoke"
+	"go.uber.org/zap"
+)
+
+func (np *Processor) processEmit() {
+	index := np.irList.Index()
+	if index < 0 {
+		np.log.Info("passive mode, ignore gas emission event")
+		return
+	} else if int(index) >= len(np.alphabetContracts) {
+		np.log.Debug("node is out of alphabet range, ignore gas emission event",
+			zap.Int32("index", index))
+		return
+	}
+
+	err := invoke.AlphabetEmit(np.morphClient, np.alphabetContracts[index])
+	if err != nil {
+		np.log.Warn("can't invoke alphabet emit method")
+	}
+}