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/astconv/mod.rs

@@ -2715,7 +2715,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let hir = tcx.hir();
 
         let hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), ident, .. }) =
-            hir.get(fn_hir_id)
+            tcx.hir_node(fn_hir_id)
         else {
             return None;
         };