Auto merge of #32810 - brson:relnotes, r=brson
Auto merge of #32810 - brson:relnotes, r=brson

Release notes for 1.8

cc @steveklabnik to me the highlights are compound assignment overloading, 32-bit MSVC builds being ready for use, and the cargo improvements.

[Rendered](https://github.com/brson/rust/blob/relnotes/RELEASES.md).

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