Add support for generic structs derriving InputObject and SimpleObject

[alisenai]

Description

Allows for generic structs which derive SimpleObject and InputObject to compile. For example:

#[derive(SimpleObject, InputObject)]
#[graphql(concrete(name = "MyObjectU32", params(u32)))]
#[graphql(concrete(name = "MyObjectString", params(String)))]
#[allow(dead_code)]
struct MyObject<T: InputType + OutputType> {
    a: T
}

Currently, this code generates the following error:

error[E0592]: duplicate definitions with name `__internal_create_type_info`
   --> tests/input_object.rs:412:14
    |
412 |     #[derive(SimpleObject, InputObject)]
    |              ^^^^^^^^^^^^  ----------- other definition for `__internal_create_type_info`
    |              |
    |              duplicate definitions for `__internal_create_type_info`

Please note that I have very little experience with this codebase outside of the public interface.

[sunli829]

Thanks! 🙂