auto merge of #20117 : lfairy/rust/rename-include-bin, r=alexcrichton

According to [RFC 344][], methods that return `&[u8]` should have names ending in `bytes`. Though `include_bin!` is a macro not a method, it seems reasonable to follow the convention anyway.

We keep the old name around for now, but trigger a deprecation warning when it is used.

[RFC 344]: https://github.com/rust-lang/rfcs/blob/master/text/0344-conventions-galore.md

[breaking-change]