hir: Simplify hir_owner_nodes query

The query accept arbitrary DefIds, not just owner DefIds.
The return can be an `Option` because if there are no nodes, then it doesn't matter whether it's due to NonOwner or Phantom.
Also rename the query to `opt_hir_owner_nodes`.

compiler/rustc_incremental/src/assert_dep_graph.rs

@@ -131,7 +131,7 @@ impl<'tcx> IfThisChanged<'tcx> {
                     None => DepNode::from_def_path_hash(
                         self.tcx,
                         def_path_hash,
-                        dep_kinds::hir_owner_nodes,
+                        dep_kinds::opt_hir_owner_nodes,
                     ),
                     Some(n) => {
                         match DepNode::from_label_string(self.tcx, n.as_str(), def_path_hash) {

compiler/rustc_incremental/src/persist/dirty_clean.rs

@@ -57,8 +57,8 @@ const BASE_FN: &[&str] = &[
 
 /// DepNodes for Hir, which is pretty much everything
 const BASE_HIR: &[&str] = &[
-    // hir_owner_nodes should be computed for all nodes
-    label_strs::hir_owner_nodes,
+    // opt_hir_owner_nodes should be computed for all nodes
+    label_strs::opt_hir_owner_nodes,
 ];
 
 /// `impl` implementation of struct/trait