rustdoc: missing docs for core::ptr::{copy, copy_nonoverlapping, write_bytes} #64539
Description
The copy, copy_nonoverlapping and write_bytes methods are exposed both via core::ptr and std::ptr. In fact, std::ptr as just a re-export of core::ptr.
However, when comparing the two pages, core::ptr is missing a few items compared to std::ptr: copy, copy_nonoverlapping and write_bytes for some reason are not shown as "functions".
I just realized that thy are shown as "reexports". So likely I could have made rust-lang/nomicon#165 link to the versions in core::intrinsics instead. But we don't actually want people to use those paths, they are available on stable only due to a bug. We'd prefer if people used these symbols through ptr, but then it seems we have to link to std::ptr, which is somewhat annoying.