[#401] control: Serve DropObjects RPC

Re-compile protobuf definition of Control service. Implement required
messages on DropObjects RPC request and response messages. Implement
`DropObjects` method on Control service server of the node. Use
`StorageEngine.Delete` method as a deleted object handler on server.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/control/server/server.go

@@ -47,6 +47,8 @@ type cfg struct {
 	netMapSrc netmap.Source
 
 	nodeState NodeState
+
+	delObjHandler DeletedObjectHandler
 }
 
 func defaultCfg() *cfg {
@@ -103,3 +105,11 @@ func WithNodeState(state NodeState) Option {
 		c.nodeState = state
 	}
 }
+
+// WithDeletedObjectHandler returns option to function
+// which is called on the objects being deleted.
+func WithDeletedObjectHandler(h DeletedObjectHandler) Option {
+	return func(c *cfg) {
+		c.delObjHandler = h
+	}
+}