fix: rename non send resources

[pietrosophya]

Objective

Rename non-send resources more consistently inside the crate.
Rewrite some docs to use "[NonSendRes] resource" instead of [!Send]
Rewrite some docs to use "[NonSendRes] resource" instead of "non-send resource"

Migration Guide

• Rename NonSend to NonSendRes
• Rename NonSendMut to NonSendResMut
• Use World::contains_non_send_resource in place of World::contains_non_send

[mockersf]

I would prefer to remove all mention of resource from NonSend methods and docs.

The fact that NonSend is kinda using resources in the implementation is an implementation detail, will probably soon change, and is not helpful to the user.

[pietrosophya]

I still think they could be considered resources (like a filesystem, a network, a printer, or even corn or pasta), because they are "things" needed to make the world run.

If not Resource, what could be another good noun? NonSend is not a noun, and although clear to expert rust users, it's confusing (I'm pretty sure I can speak for many Bevy users here).

[alice-i-cecile]

I think we need a better noun for them: they aren't resources in the sense of Resource, and are likely to drift even further away. Data maybe?

[MrGVSV]

I think we need a better noun for them: they aren't resources in the sense of Resource, and are likely to drift even further away.

I think the problem is they're just too similar to what resources are even if given a different label. A "resource" is really just a convenient way to store a "single global instance of some data" (to quote the Cheatbook— not because it speaks for Bevy's views but because it sorta shows how the community sees these types). NonSend does this as well but just changes how a system is run.

They aren't a "resource" in that T has to derive Resource, but to me that's the implementation detail. NonSend could just as easily require a NonSendResource derive or something.

Granted, I’m not familiar with the discussion around the ultimate goals for handling non-send data so I could be waaayyy off haha. But imo if it still has the purpose of being a "thread-local/non-send global singleton" then it's still kind of a "resource" (especially if you access it via system parameter like you would a regular Resource).

So I personally prefer the rename presented in this PR.

[pietrosophya]

@alice-i-cecile what should be the next steps for this PR (to approve or discard it)?

[BenjaminBrienen]

Relevant discussion: https://discord.com/channels/691052431525675048/1331346448662397059/1331813217537757238

[alice-i-cecile]

Closing this out: I agree that this isn't a good name, but NonSend data needs a bigger refactor and it's not worth the churn for now.