Rollup merge of #133023 - samestep:hir-stats-total-count, r=nnethercote

Merge `-Zhir-stats` into `-Zinput-stats`

Currently `-Z hir-stats` prints the size and count of various kinds of nodes, and the total size of all the nodes it counted, but not the total count of nodes. So, before this PR:

```
$ git clone https://github.com/BurntSushi/ripgrep
$ cd ripgrep
$ cargo +nightly rustc -- -Z hir-stats
ast-stats-1 PRE EXPANSION AST STATS
ast-stats-1 Name                Accumulated Size         Count     Item Size
ast-stats-1 ----------------------------------------------------------------
ast-stats-1 ...
ast-stats-1 ----------------------------------------------------------------
ast-stats-1 Total                 93_576
ast-stats-1
ast-stats-2 POST EXPANSION AST STATS
ast-stats-2 Name                Accumulated Size         Count     Item Size
ast-stats-2 ----------------------------------------------------------------
ast-stats-2 ...
ast-stats-2 ----------------------------------------------------------------
ast-stats-2 Total              2_430_648
ast-stats-2
hir-stats HIR STATS
hir-stats Name                Accumulated Size         Count     Item Size
hir-stats ----------------------------------------------------------------
hir-stats ...
hir-stats ----------------------------------------------------------------
hir-stats Total              3_678_512
hir-stats
```

For consistency, this PR adds a total for the count as well:

```
$ cargo +stage1 rustc -- -Z hir-stats
ast-stats-1 PRE EXPANSION AST STATS
ast-stats-1 Name                Accumulated Size         Count     Item Size
ast-stats-1 ----------------------------------------------------------------
ast-stats-1 ...
ast-stats-1 ----------------------------------------------------------------
ast-stats-1 Total                 93_576                 1_877
ast-stats-1
ast-stats-2 POST EXPANSION AST STATS
ast-stats-2 Name                Accumulated Size         Count     Item Size
ast-stats-2 ----------------------------------------------------------------
ast-stats-2 ...
ast-stats-2 ----------------------------------------------------------------
ast-stats-2 Total              2_430_648                48_625
ast-stats-2
hir-stats HIR STATS
hir-stats Name                Accumulated Size         Count     Item Size
hir-stats ----------------------------------------------------------------
hir-stats ...
hir-stats ----------------------------------------------------------------
hir-stats Total              3_678_512                73_418
hir-stats
```

I wasn't sure if I was supposed to update `tests/ui/stats/hir-stats.stderr` to reflect this. I ran it locally, thinking it would fail, but it didn't:

```
$ ./x test tests/ui/stats
...

running 2 tests
i.

test result: ok. 1 passed; 0 failed; 1 ignored; 0 measured; 17949 filtered out
```

Also: is there a reason `-Z hir-stats` and `-Z input-stats` both exist? The former seems like it should completely supercede the latter. But strangely, the two give very different numbers for node counts:

```
$ cargo +nightly rustc -- -Z input-stats
...
Lines of code:             483
Pre-expansion node count:  2386
Post-expansion node count: 63844
```

That's a 30% difference in this case. Is it intentional that these numbers are so different? I see comments for both saying that they are merely approximations and should not be expected to be correct:

bd0826a452/compiler/rustc_ast_passes/src/node_count.rs (L1)

bd0826a452/compiler/rustc_passes/src/hir_stats.rs (L1-L3)

compiler/rustc_passes/src/input_stats.rs

@@ -126,6 +126,7 @@ impl<'k> StatCollector<'k> {
         });
 
         let total_size = nodes.iter().map(|(_, node)| node.stats.count * node.stats.size).sum();
+        let total_count = nodes.iter().map(|(_, node)| node.stats.count).sum();
 
         eprintln!("{prefix} {title}");
         eprintln!(
@@ -167,7 +168,13 @@ impl<'k> StatCollector<'k> {
             }
         }
         eprintln!("{prefix} ----------------------------------------------------------------");
-        eprintln!("{} {:<18}{:>10}", prefix, "Total", to_readable_str(total_size));
+        eprintln!(
+            "{} {:<18}{:>10}        {:>14}",
+            prefix,
+            "Total",
+            to_readable_str(total_size),
+            to_readable_str(total_count),
+        );
         eprintln!("{prefix}");
     }
 }

compiler/rustc_passes/src/lib.rs

@@ -27,7 +27,7 @@ pub mod entry;
 mod errors;
 #[cfg(debug_assertions)]
 pub mod hir_id_validator;
-pub mod hir_stats;
+pub mod input_stats;
 mod lang_items;
 pub mod layout_test;
 mod lib_features;