Auto merge of #4216 - phansch:replace_nodeset, r=matthiaskrgr
Auto merge of #4216 - phansch:replace_nodeset, r=matthiaskrgr

Refactor: Replace NodeSet with HirIdSet

This saves us one HirId -> NodeId conversion.

changelog: none

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