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)
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