Remove -Zperf-stats.

The included measurements have varied over the years. At one point there
were quite a few more, but #49558 deleted a lot that were no longer
used. Today there's just four, and it's a motley collection that doesn't
seem particularly valuable.

I think it has been well and truly subsumed by self-profiling, which
collects way more data.

compiler/rustc_driver_impl/src/lib.rs

@@ -496,10 +496,6 @@ fn run_compiler(
             linker.link()?
         }
 
-        if sess.opts.unstable_opts.perf_stats {
-            sess.print_perf_stats();
-        }
-
         if sess.opts.unstable_opts.print_fuel.is_some() {
             eprintln!(
                 "Fuel used by {}: {}",