Auto merge of #53397 - varkor:feature-collector-expand-visitor, r=nikomatsakis
Auto merge of #53397 - varkor:feature-collector-expand-visitor, r=nikomatsakis

Visit all attributes for feature collection

Previously feature attributes were just collected on item-like "things" as well as exported macros and crate attributes. This ignored some places feature attributes could be specified, such as on enum variants.

Fixes https://github.com/rust-lang/rust/issues/53391.

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