Investigate support for other generic Sway types

[ra0x3]

• Might require a bit of investigation
• Whilst working on chore: add sway app abi tests #1341 I noticed that we currently don't support other generic Sway types
• While we do support some generic types (i.e., Vec<T> (when it's ready from SDK), Option<T>) there are other generics we don't support:

Example:

enum GenericEnum<T> {
   ValueOne: T
}

struct GenericStruct<T> {
    id: u8,
    value: T,
}

fn some_function() {
    let s = GenericStruct<u64>{ id: 1, value: 2};
    let e = GenericEnum::<bool>::ValueOne(true);
}

• Technically, if the generic T of some type is indexable, then the entire type should be indexable
• We would maybe have to think about outlining some constraints/parameters around what we will/won't support