`bevy_platform::prelude` items are not available in other modules

[urben1680]

I noticed that in the prelude module of bevy_platform, there are items exclusively there. That is uncommon as using prelude is generally optional to get a quick import done.

https://dev-docs.bevy.org/bevy_platform/prelude/index.html

The docs of prelude here seem to try to fulfill another purpose, migrating from std to no_std, I guess? We might then maybe want to rename the module to something else.