Auto merge of #78415 - tgnottingham:expn_id_tag_hash, r=Aaron1011
Auto merge of #78415 - tgnottingham:expn_id_tag_hash, r=Aaron1011

rustc_span: avoid hashing ExpnId tag when using cached hash

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