Rollup merge of #40333 - tbu-:pr_doc_ptr_write, r=alexcrichton
Rollup merge of #40333 - tbu-:pr_doc_ptr_write, r=alexcrichton

Clarify handling of `src` in `ptr::write`

Fixes #39733.

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