Dont check stability for items that are not pub to universe.
Dont check stability for items that are not pub to universe.

Includes special case handling for trait methods.

Fix #38412.

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