Rollup merge of #105558 - Nilstrieb:less-spam-hir-tree, r=cjgillot

Reduce HIR debug output

HIR debug output is currently very verbose, especially when used with the alternate (`#`) flag. This commit reduces the amount of noisy newlines by forcing a few small key types to stay on one line, which makes the output easier to read and scroll by.

```
$ rustc +after hello_world.rs -Zunpretty=hir-tree | wc -l
582
$ rustc +before hello_world.rs -Zunpretty=hir-tree | wc -l
932
```

src/test/ui/thir-tree.stdout

@@ -32,12 +32,7 @@ Thir {
             kind: Scope {
                 region_scope: Node(2),
                 lint_level: Explicit(
-                    HirId {
-                        owner: OwnerId {
-                            def_id: DefId(0:3 ~ thir_tree[8f1d]::main),
-                        },
-                        local_id: 2,
-                    },
+                    HirId(DefId(0:3 ~ thir_tree[8f1d]::main).2),
                 ),
                 value: e0,
             },