Implement Vec in storage, potentially starting with a new type StorageVec

[mohammadfawaz]

Vec<T> cannot be used in storage today because its data is heap data. Ideally, we would be able to have a type Vec<T> that behaves differently depending on whether it's declared inside a storage block or outside it.

• If declared outside a storage block, then Vec<T> and its methods would behave exactly as they do today.
• If declared inside a storage block, then Vec<T> and its methods would store and access its data from storage instead of the heap.

A good starting point however is to implement StorageVec<T> with the same API as Vec<T>, but uses persistent storage instead of the heap.

[SwayStar123]

I would like to start implementing a seperate StorageVec type right now