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_mir_build/src/build/mod.rs

@@ -572,7 +572,7 @@ fn construct_const<'a, 'tcx>(
     let hir_id = tcx.local_def_id_to_hir_id(def);
 
     // Figure out what primary body this item has.
-    let (span, const_ty_span) = match tcx.hir().get(hir_id) {
+    let (span, const_ty_span) = match tcx.hir_node(hir_id) {
         Node::Item(hir::Item {
             kind: hir::ItemKind::Static(ty, _, _) | hir::ItemKind::Const(ty, _, _),
             span,