Tracking issue for renaming crate dependencies

[alexcrichton]

This is a tracking issue for the package key in the [dependencies] section.

First introduced in #4953 and the original tracking issue was #1311. Known issues are:

• What to do about --features on the command line? Does --features foo/bar imply the package foo or the crate that's renamed to foo? We probably want the latter, and that's probably buggy right now.

[matklad]

Argh, I've accidentally created #5653 (comment). Closing in favor of that, it has more info.