Rollup merge of #29416 - brson:relnotes, r=alexcrichton
Rollup merge of #29416 - brson:relnotes, r=alexcrichton

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

More highlights would be good. I intend to go through and hyperlink all the APIs still.

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