Move some methods from tcx.hir() to tcx

Renamings:
- find -> opt_hir_node
- get -> hir_node
- find_by_def_id -> opt_hir_node_by_def_id
- get_by_def_id -> hir_node_by_def_id

Fix rebase changes using removed methods

Use `tcx.hir_node_by_def_id()` whenever possible in compiler

Fix clippy errors

Fix compiler

Apply suggestions from code review

Co-authored-by: Vadim Petrochenkov <vadim.petrochenkov@gmail.com>

Add FIXME for `tcx.hir()` returned type about its removal

Simplify with with `tcx.hir_node_by_def_id`

compiler/rustc_passes/src/naked_functions.rs

@@ -35,7 +35,7 @@ fn check_mod_naked_functions(tcx: TyCtxt<'_>, module_def_id: LocalModDefId) {
             continue;
         }
 
-        let (fn_header, body_id) = match tcx.hir().get_by_def_id(def_id) {
+        let (fn_header, body_id) = match tcx.hir_node_by_def_id(def_id) {
             hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(sig, _, body_id), .. })
             | hir::Node::TraitItem(hir::TraitItem {
                 kind: hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)),