shim: change ttrpcService and ttrpcServerOptioner to exported interfaces

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

runtime/v2/example/example.go

@@ -77,6 +77,10 @@ func newTaskService(ctx context.Context, publisher shim.Publisher, sd shutdown.S
 	return &exampleTaskService{}, nil
 }
 
+var (
+	_ = shim.TTRPCService(&exampleTaskService{})
+)
+
 type exampleTaskService struct {
 }