rustc: Remove CrateStore::crates as a method

This commit moves the `crates` method to a query and then migrates all callers
to use a query instead of the now-renamed `crates_untracked` method where
possible.

Closes #41417

src/librustdoc/clean/inline.rs

@@ -236,7 +236,7 @@ pub fn build_impls(cx: &DocContext, did: DefId) -> Vec<clean::Item> {
 
     cx.populated_all_crate_impls.set(true);
 
-    for cnum in tcx.sess.cstore.crates() {
+    for &cnum in tcx.crates().iter() {
         for did in tcx.all_trait_implementations(cnum).iter() {
             build_impl(cx, *did, &mut impls);
         }

src/librustdoc/clean/mod.rs

@@ -131,7 +131,7 @@ impl<'a, 'tcx> Clean<Crate> for visit_ast::RustdocVisitor<'a, 'tcx> {
         }
 
         let mut externs = Vec::new();
-        for cnum in cx.sess().cstore.crates() {
+        for &cnum in cx.tcx.crates().iter() {
             externs.push((cnum, cnum.clean(cx)));
             // Analyze doc-reachability for extern items
             LibEmbargoVisitor::new(cx).visit_lib(cnum);