hir: Remove opt_local_def_id_to_hir_id and opt_hir_node_by_def_id

Also replace a few `hir_node()` calls with `hir_node_by_def_id()`

compiler/rustc_passes/src/entry.rs

@@ -127,7 +127,7 @@ fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) -> Option<(DefId,
         {
             // non-local main imports are handled below
             if let Some(def_id) = def_id.as_local()
-                && matches!(tcx.opt_hir_node_by_def_id(def_id), Some(Node::ForeignItem(_)))
+                && matches!(tcx.hir_node_by_def_id(def_id), Node::ForeignItem(_))
             {
                 tcx.dcx().emit_err(ExternMain { span: tcx.def_span(def_id) });
                 return None;