extend self-test log processing

[aritas1]

this adds metrics for monitoring the latest self-tests execution time.

also fix the missing smartctl_device_self_test_log_count metric due to missing --log=selftest argument.

[robbat2]

This should accept either standard or extended. Some args & device combinations only have one of them. The layout of the json struct is the same.

[robbat2]

this is implicitly trusting that the tests appear in newest to oldest order. I don't know if I trust drives enough for that.

[robbat2]

this is not correct, from one of my systems:

"status": {
"value": 41,
"string": "Interrupted (host reset)",
"remaining_percent": 90
}

status.passeed is NOT present in this case.

I don't have any SATA drives w/ failing checks to compare presentlyy, but I worry they are also non-zero.

[robbat2]

Ok, it's definetly in need of work; also in the smartctl sources:

  std::string msgstat;
  switch (test_status >> 4) {
    case 0x0: msgstat = "Completed without error";       break;
    case 0x1: msgstat = "Aborted by host";               break;
    case 0x2: msgstat = "Interrupted (host reset)";      break;
    case 0x3: msgstat = "Fatal or unknown error";        break;
    case 0x4: msgstat = "Completed: unknown failure";    break;
    case 0x5: msgstat = "Completed: electrical failure"; break;
    case 0x6: msgstat = "Completed: servo/seek failure"; break;
    case 0x7: msgstat = "Completed: read failure";       break;
    case 0x8: msgstat = "Completed: handling damage??";  break;
    case 0xf: msgstat = "Self-test routine in progress"; break;
    default:  msgstat = strprintf("Unknown status (0x%x)", test_status >> 4);
  }

So if it's 0xF then skip it as running; otherwise map the error.

[robbat2]

from smartctl sources:

  switch (test_type) {
    case 0x00: msgtest = "Offline";            break;
    case 0x01: msgtest = "Short offline";      break;
    case 0x02: msgtest = "Extended offline";   break;
    case 0x03: msgtest = "Conveyance offline"; break;
    case 0x04: msgtest = "Selective offline";  break;
    case 0x7f: msgtest = "Abort offline test"; break;
    case 0x81: msgtest = "Short captive";      break;
    case 0x82: msgtest = "Extended captive";   break;
    case 0x83: msgtest = "Conveyance captive"; break;
    case 0x84: msgtest = "Selective captive";  break;
    default:
      if ((0x40 <= test_type && test_type <= 0x7e) || 0x90 <= test_type)
        msgtest = strprintf("Vendor (0x%02x)", test_type);
      else
        msgtest = strprintf("Reserved (0x%02x)", test_type);
  }