Make all dist functions and structs crate-private and cleanup unused functions

[0xPoe]

part of #2730

[0xPoe]

@kinnison Thanks for your review!

Regarding the use of pub(crate) in the pub(crate) structure I understand that it is useful? Because the visibility of the fields of a pub(crate) structure is private by default and cannot be accessed by other mods in the same crate. So we can use pub(crate)? If we use pub, then other crates will be able to use it. This would result in the accessibility being amplified?

An example of a compilation error that does not use pub(crate): https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=ece1d5cb3da661daf651d6dbd575d21b

An example of a successful compilation using pub(crate): https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=5dc0ff67c55081d1ffec5fd0666bc6f3

I'm not sure if I'm understanding this correctly?

[0xPoe]

@kinnison ping~

Could you please take a look? Thanks!

[kinnison]

Hi, the thing is that with the struct being pub(crate) there's no difference in meaning between pub and pub(crate) on the fields. Except the latter implies that the crate has privileged and special knowledge of the interior of the structure which frankly it doesn't. I'd prefer pub(crate) on the struct, and then just plain pub on the fields. There can be no access amplification because nothing outside of the crate can address the struct type at all.

[0xPoe]

Hi, the thing is that with the struct being pub(crate) there's no difference in meaning between pub and pub(crate) on the fields. Except the latter implies that the crate has privileged and special knowledge of the interior of the structure which frankly it doesn't. I'd prefer pub(crate) on the struct, and then just plain pub on the fields. There can be no access amplification because nothing outside of the crate can address the struct type at all.

I modified them all to pub. Thanks for you review!