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/interpret/validity.rs

@@ -227,7 +227,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                         // Sometimes the index is beyond the number of upvars (seen
                         // for a coroutine).
                         let var_hir_id = captured_place.get_root_variable();
-                        let node = self.ecx.tcx.hir().get(var_hir_id);
+                        let node = self.ecx.tcx.hir_node(var_hir_id);
                         if let hir::Node::Pat(pat) = node {
                             if let hir::PatKind::Binding(_, _, ident, _) = pat.kind {
                                 name = Some(ident.name);