Rollup merge of #62344 - matklad:simplify-option, r=sfackler
Rollup merge of #62344 - matklad:simplify-option, r=sfackler

simplify Option::get_or_insert

I am pretty sure that the optimized result will be the same, and it's one `unsafe` less in the stdlib!

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