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_hir_analysis/src/check/mod.rs

@@ -130,7 +130,7 @@ fn get_owner_return_paths(
 ) -> Option<(LocalDefId, ReturnsVisitor<'_>)> {
     let hir_id = tcx.local_def_id_to_hir_id(def_id);
     let parent_id = tcx.hir().get_parent_item(hir_id).def_id;
-    tcx.hir().find_by_def_id(parent_id).and_then(|node| node.body_id()).map(|body_id| {
+    tcx.opt_hir_node_by_def_id(parent_id).and_then(|node| node.body_id()).map(|body_id| {
         let body = tcx.hir().body(body_id);
         let mut visitor = ReturnsVisitor::default();
         visitor.visit_body(body);