[FEA]Custom generated name

### Why

I'd like to static link many models to my program, and call `predict` function in different threads instead of using the provided `Predictor`.

### Problem

But all the generated name is same.

### current workaround

I have to do some *"search and replace"* after generating source code.

### Expected solution

It's pretty good if I can custom the generated name. Adding prefix or suffix is enough, I think.