Implement basic type inference for generic structs and functions

[edg-l]

mod MyMod {
    struct GenericStruct<T> {
        a: T,
        b: u32,
    }

    pub fn main() -> i32 {
        let value: GenericStruct<i32> = GenericStruct::<i32> {
            a: 2,
            b: 4,
        };

        return value.a;
    }
}

Currently for generic structs and functions, the types need to be specified while they could be reasonably infered by the arguments used.

So this would turn into

mod MyMod {
    struct GenericStruct<T> {
        a: T,
        b: u32,
    }

    pub fn main() -> i32 {
        // Maybe we can even infer let types completely too.
        let value: GenericStruct<i32> = GenericStruct {
            a: 2,
            b: 4,
        };

        return value.a;
    }
}