Rollup merge of #34875 - frewsxcv:std-slice-struct, r=GuillaumeGomez
Rollup merge of #34875 - frewsxcv:std-slice-struct, r=GuillaumeGomez

Indicate where `std::slice` structs originate from.

None

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