Rollup merge of #33705 - lqd:rustdoc-version-tooltip, r=GuillaumeGomez
Rollup merge of #33705 - lqd:rustdoc-version-tooltip, r=GuillaumeGomez

rustdoc: Make the #[stable(since)] version attribute clearer with a tooltip

Rustdoc's new 'since' version placement only shows the version number in which the item was marked stable. This gains space but might make the meaning of this version string less clear in the docs, so I tried to bring some explicitness in a tooltip.

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