shim: change ttrpcService and ttrpcServerOptioner to exported interfaces

Signed-off-by: Iceber Gu <wei.cai-nat@daocloud.io>

integration/failpoint/cmd/containerd-shim-runc-fp-v1/plugin_linux.go

@@ -72,9 +72,12 @@ func init() {
 			}, nil
 		},
 	})
-
 }
 
+var (
+	_ = shim.TTRPCServerOptioner(&taskServiceWithFp{})
+)
+
 type taskServiceWithFp struct {
 	fps   map[string]*failpoint.Failpoint
 	local taskapi.TaskService