[Bug] cpu usage is not accurate

[icankeep]

now

  if config.track_cpu_percent:
      cpu_count = psutil.cpu_count()
      cpu_percent = await self._get_cpu_percent(all_processes)

      if config.cpu_limit != 0:
          limits["cpu"] = {"cpu": config.cpu_limit}
          if config.cpu_warning_threshold != 0:
              limits["cpu"]["warn"] = (config.cpu_limit - cpu_percent) < (
                  config.cpu_limit * config.cpu_warning_threshold
              )

      metrics.update(cpu_percent=cpu_percent, cpu_count=cpu_count)

Why not use psutil's cpu usage directly?

e.g.

psutil.cpu_percent()

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