Coding style: add a section on list ordering.

[jrvanwhy]

I've been keeping a lot of things (such as Cargo.toml package lists and mod declarations) in alphabetical order. This adds that preference to the style guide.

Rendered

[bradjc]

I'm pretty opposed to this, but I won't stand in the way. If this kind of thing isn't enforced by a tool ala rustfmt, I don't see how this is a good use of developer effort. Just my 2¢.

I do think it is reasonable to say this is the expected style but not enforce it on each PR, and then just open PRs like this one from time to time. I do that with a few things in tockland.

Also, maybe this is coming? rust-lang/rustfmt#5240 I didn't read too closely.

[lschuermann]

Whenever I walk across a large list such as workspace and it's not sorted it makes me sad.

[jrvanwhy]

I do think it is reasonable to say this is the expected style but not enforce it on each PR, and then just open PRs like this one from time to time. I do that with a few things in tockland.

I'm okay with this plan, since we don't have a way to enforce it automatically.

[jrvanwhy]

I will merge as-is, but we won't proactively enforce this during PR reviews, unless doing so would avoid a merge conflict.