perf script: Print information about per-event-dump files

For a file generated by "perf sched record sleep 50":

  # perf script --per-event-dump
  [ perf script: Wrote 23.121 MB perf.data.sched:sched_switch.dump (206015 samples) ]
  [ perf script: Wrote 0.000 MB perf.data.sched:sched_stat_wait.dump (0 samples) ]
  [ perf script: Wrote 0.000 MB perf.data.sched:sched_stat_sleep.dump (0 samples) ]
  [ perf script: Wrote 0.000 MB perf.data.sched:sched_stat_iowait.dump (0 samples) ]
  [ perf script: Wrote 17.680 MB perf.data.sched:sched_stat_runtime.dump (129342 samples) ]
  [ perf script: Wrote 0.000 MB perf.data.sched:sched_process_fork.dump (24 samples) ]
  [ perf script: Wrote 11.328 MB perf.data.sched:sched_wakeup.dump (106770 samples) ]
  [ perf script: Wrote 0.000 MB perf.data.sched:sched_wakeup_new.dump (24 samples) ]
  [ perf script: Wrote 2.477 MB perf.data.sched:sched_migrate_task.dump (20434 samples) ]
  #

Similar to what is generated by 'perf record'.

Based-on-a-patch-by: yuzhoujian <yuzhoujian@didichuxing.com>
Suggested-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1508921599-10832-3-git-send-email-yuzhoujian@didichuxing.com
Link: http://lkml.kernel.org/n/tip-xuketkkjuk2c0qz546ypd1u7@git.kernel.org


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