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_const_eval/src/const_eval/fn_queries.rs

@@ -33,7 +33,7 @@ pub fn is_parent_const_impl_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
 /// return if it has a `const` modifier. If it is an intrinsic, report whether said intrinsic
 /// has a `rustc_const_{un,}stable` attribute. Otherwise, return `Constness::NotConst`.
 fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness {
-    let node = tcx.hir().get_by_def_id(def_id);
+    let node = tcx.hir_node_by_def_id(def_id);
 
     match node {
         hir::Node::Ctor(_)