Queryify is_doc_hidden

It came up hot on some profiling of rustdoc I did, so hopefully turning
it into a query will help.

compiler/rustc_middle/src/ty/mod.rs

@@ -41,7 +41,7 @@ use rustc_macros::HashStable;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_session::cstore::CrateStoreDyn;
 use rustc_span::symbol::{kw, Ident, Symbol};
-use rustc_span::{sym, Span};
+use rustc_span::Span;
 use rustc_target::abi::Align;
 
 use std::hash::Hash;
@@ -2125,14 +2125,6 @@ impl<'tcx> TyCtxt<'tcx> {
         self.sess.contains_name(&self.get_attrs(did), attr)
     }
 
-    /// Determines whether an item is annotated with `doc(hidden)`.
-    pub fn is_doc_hidden(self, did: DefId) -> bool {
-        self.get_attrs(did)
-            .iter()
-            .filter_map(|attr| if attr.has_name(sym::doc) { attr.meta_item_list() } else { None })
-            .any(|items| items.iter().any(|item| item.has_name(sym::hidden)))
-    }
-
     /// Returns `true` if this is an `auto trait`.
     pub fn trait_is_auto(self, trait_def_id: DefId) -> bool {
         self.trait_def(trait_def_id).has_auto_impl