Feature: Support Complex Generic Types in Contract Storage

[0xNeshi]

This specifically refers to upgrading #[storage] attribute. The following code compiles just fine:

pub struct EnumerableSet<T: SimpleStorageType<'static>>
where
    for<'a> <T as StorageType>::Wraps<'a>: StorageKey + Copy + Clone,
    Self: 'static,
{
    /// Values in the set.
    values: StorageVec<T>,
    /// Value -> Index of the value in the `values` array.
    positions: StorageMap<<T as StorageType>::Wraps<'static>, StorageU256>,
}

But adding the #[storage] attribute introduces compiler errors:

#[storage]
// ^^^^^^
// the trait bound `<T as stylus_sdk::prelude::StorageType>::Wraps<'static>: StorageKey` is not satisfied the trait `StorageKey` is not implemented for `<T as stylus_sdk::prelude::StorageType>::Wraps<'static>`
// map.rs(15, 26): required by a bound in `StorageMap`
pub struct EnumerableSet<T: SimpleStorageType<'static>>
where
    for<'a> <T as StorageType>::Wraps<'a>: StorageKey + Copy + Clone,
    Self: 'static,
{
    /// Values in the set.
    values: StorageVec<T>,
    /// Value -> Index of the value in the `values` array.
    positions: StorageMap<<T as StorageType>::Wraps<'static>, StorageU256>,
    //                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    //                the trait bound `<T as stylus_sdk::prelude::StorageType>::Wraps<'static>: StorageKey` is not satisfied the trait `StorageKey` is not implemented for `<T as stylus_sdk::prelude::StorageType>::Wraps<'static>` 
    //                map.rs(15, 26): required by a bound in `StorageMap`
    //                file_name.rs(23, 56): consider introducing a `where` clause, but there might be an alternative better way to express this requirement: ` where <T as stylus_sdk::prelude::StorageType>::Wraps<'static>: StorageKey`
}