use consistent terminology to refer to containers/collections

[thestinger]

There is a container module in std and a separate collections crate. This should be consistent, and the traits should be in the same place as the containers.

[pnkfelix]

The current set of traits in std::container are arguably not currently expressive enough to actually use in writing generic code.

So something needs to be done about that, because as it stands right now, it seems like container is not pulling its weight. We should either revamp the API's there, or remove container.

Assigning 1.0, P-backcompat-libs.

[thestinger]

It does work for allowing a graph library to make use of arbitrary set and map containers. It can't abstract over both in-memory and on-disk or virtual data structures and I think that's a fundamental limitation of Rust's trait system. It's simply not as expressive as C++ templates.

[huonw]

Reading it now, I think the triage missed the main point of this bug: the inconsistency of the name containers vs. the name collections.

[aturon]

I strongly agree that the Containers traits, whatever they wind up being called, need to be revisited or possibly removed. Should that concern be opened as a separate issue?