rustdoc: Add doc snippets for trait impls, with a read more link
rustdoc: Add doc snippets for trait impls, with a read more link

Fixes #33672

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