Support arrays

The appropriate representation for `MaybeUninit<[T; N]>` is [`[MaybeUninit<T>; N]`](https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#initializing-an-array-element-by-element). An array specific builder should be created so that an uninitialized array isn't possible while also allowing piece-meal setting of their fields.