Auto merge of #30939 - shepmaster:btreeset-insert-return-value, r=alexcrichton
Auto merge of #30939 - shepmaster:btreeset-insert-return-value, r=alexcrichton

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