Rollup merge of #57848 - jrvanwhy:transmute-export-doc, r=QuietMisdreavus
Rollup merge of #57848 - jrvanwhy:transmute-export-doc, r=QuietMisdreavus

Generate a documentation page for core::mem::transmute.

In `#[no_std]` environments, `std::mem::transmute` is unavailable. Searching for "core transmute" online only pulls up `core::intrinsics::transmute`, which is behind the (unstable) `core_intrinsics` feature flag. Users wishing to use transmute in `#[no_std]` environments typically should use `core::mem::transmute` instead, as it is stable. This documentation makes `core::mem::transmute` discoverable.

aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust