perf parse-events: Add debug dump of evlist if reordered

Add debug verbose output to show how evsels were reordered by
parse_events__sort_events_and_fix_groups(). For example:

```
$ perf record -v -e '{instructions,cycles}' true
Using CPUID GenuineIntel-6-B7-1
WARNING: events were regrouped to match PMUs
evlist after sorting/fixing: '{cpu_atom/instructions/,cpu_atom/cycles/},{cpu_core/instructions/,cpu_core/cycles/}'
```

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Dr. David Alan Gilbert <linux@treblig.org>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Levi Yun <yeoreum.yun@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Weilin Wang <weilin.wang@intel.com>
Link: https://lore.kernel.org/r/20250402201549.4090305-6-irogers@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>