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/hir_wf_check.rs

@@ -122,7 +122,7 @@ fn diagnostic_hir_wf_check<'tcx>(
     // We will walk 'into' this type to try to find
     // a more precise span for our predicate.
     let tys = match loc {
-        WellFormedLoc::Ty(_) => match hir.get(hir_id) {
+        WellFormedLoc::Ty(_) => match tcx.hir_node(hir_id) {
             hir::Node::ImplItem(item) => match item.kind {
                 hir::ImplItemKind::Type(ty) => vec![ty],
                 hir::ImplItemKind::Const(ty, _) => vec![ty],