Complex return type in cross contract calls

[rjnrohit]

Right now, the for the cross contract calls only the simple primitive returns types are supported, but for complex types such as Struct , we need to modify cairoWriter to add #[derive(Serde)] attribute to struct cairo types.

i.e

#[derive(Serde)]
struct AA_79f8c9d4 {
    x: u256,
    y: u256,
}