core: Move the collections traits to libcollections

This commit moves Mutable, Map, MutableMap, Set, and MutableSet from
`core::collections` to the `collections` crate at the top-level. Additionally,
this removes the `deque` module and moves the `Deque` trait to only being
available at the top-level of the collections crate.

All functionality continues to be reexported through `std::collections`.

[breaking-change]