Emit type arguments for generic structs/enums in the JSON ABI file and update the function selector to include those type arguments

[mohammadfawaz]

This is needed to support Vec<T> in the ABI. The struct Vec does not have data fields that actually use the type T. Therefore, the ABI won't currently have that type information that is needed by the SDK. This needs to change. Spec changes to be made as well once we're done spec-ing this out.

Note that unresolved generic types in the ABI are not allowed. However, something like this is allowed:

abi Foo {
    fn foo(v: Vec<u64>); // This `u64` should show up in the JSON ABI file
}

We may also need to update the function selector to include the type information above. This is probably needed to be consistent with how we handle non-generic types. Vec<u64> is a totally different type from Vec<bool>.

[mohammadfawaz]

Here's how this might look like in the general case:

contract;

struct Foo<T, U> {
}

struct S {
    x: u64,
    y: b256,
}

abi MyContract {
    fn test_function(f: Foo<str[3], S>) -> bool;
}

impl MyContract for Contract {
    fn test_function(f: Foo<str[3], S>) -> bool {
        true
    }
}

JSON ABI:

[
  {
    "type": "function",
    "inputs": [
      {
        "name": "f",
        "type": "struct Foo",
        "components": [],
        "typeArguments": [
          {
            "name": "T",
            "type": "str[3]",
            "components": null,
            "typeArguments": null
          },
          {
            "name": "U",
            "type": "struct S",
            "components": [
              {
                "name": "x",    
                "type": "u64",
                "components": null
                "typeArguments": null
              },
              {
                "name": "y",    
                "type": "b256",
                "components": null
                "typeArguments": null
              }
            ],
            "typeArguments": [] 
          }
        ]
      }
    ],
    "name": "test_function",
    "outputs": [
      {
        "name": "",
        "type": "bool",
        "components": null
        "typeArguments": null
      }
    ]
  }
]

Note the new field "type_arguments" which will be

• [] for structs and enums that don't have type parameters.
• null for types that are not structs or enums.
• Non-empty array otherwise.

Thoughts? @digorithm @adlerjohn

[digorithm]

@mohammadfawaz That looks reasonable to me, though implementation problems/challenges may or may not arise once we're actually implementing it on the SDK side. But at first glance, it looks simple enough!