Discussion about dropping some collections

Let's leverage instead of re-write Apple collections: https://github.com/apple/swift-collections.git

I want to add these collections by adding `swift-collections` as a dependency.

```
Deque, a double-ended queue backed by a ring buffer. Deques are range-replaceable, mutable, random-access collections.

OrderedSet, a variant of the standard Set where the order of items is well-defined and items can be arbitrarily reordered. Uses a ContiguousArray as its backing store, augmented by a separate hash table of bit packed offsets into it.

OrderedDictionary, an ordered variant of the standard Dictionary, providing similar benefits.
```

In lieu of:

- Deque
- SortedDictionary