Rollup merge of #71767 - tshepang:stack-stuff, r=jonas-schievink
Rollup merge of #71767 - tshepang:stack-stuff, r=jonas-schievink

doc: make Stack and StackElement a little pretty

Also, fix rustdoc warnings.

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