Add lint bevy_platform_alternative_exists

[DaAlbrecht]

Objective

Add new lint that checks if a given Ty was used from the std that has an equivalent in bevy_platform.

Known limitations

So far, this lint only checks structs. I think this is already useful in its current state, and I think it would be a good follow-up issue to extend this and special-case traits, FnDefs, etc.

Note to Reviewers

I often worked on this when I had small breaks so I would not recommend going through commit by commit, as I committed more to save my current state and not as a hint for reviewers.
A helpful look could be this clippy lint that I got recommended on Zulip: https://github.com/rust-lang/rust-clippy/blob/master/clippy_lints/src/std_instead_of_core.rs

• how to integrate: https://docs.rs/bevy/latest/bevy/platform/hash/index.html (we can just add: https://docs.rs/bevy/latest/bevy/platform/hash/index.html#structs)
• https://docs.rs/bevy/latest/bevy/platform/thread/index.html (I'm fine with this being a follow-up IMO)

Closes #432