Implement disk.GetDiskSerialNumber for Windows via WMI

shirou#435. Parameter should be \\.\PHYSICALDRIVEX as obtained
via `wmic diskdrive`. See also https://superuser.com/a/498109

The serial is currently returned as found via WMI, testing would be needed
by booting on Linux to check if we have the same results and probably
sort them as per https://stackoverflow.com/q/27297348/

disk/disk_windows.go

@@ -7,6 +7,7 @@ import (
 	"context"
 	"unsafe"
 
+	"github.com/StackExchange/wmi"
 	"github.com/shirou/gopsutil/internal/common"
 	"golang.org/x/sys/windows"
 )
@@ -33,6 +34,11 @@ type Win32_PerfFormattedData struct {
 	AvgDisksecPerWrite      uint64
 }
 
+type Win32_DiskDrive struct {
+	Name         string
+	SerialNumber string
+}
+
 const WaitMSec = 500
 
 func Usage(path string) (*UsageStat, error) {
@@ -159,3 +165,20 @@ func IOCounters(names ...string) (map[string]IOCountersStat, error) {
 	}
 	return ret, nil
 }
+
+func GetDiskSerialNumber(name string) string {
+	var dst []Win32_DiskDrive
+	q := wmi.CreateQuery(&dst, "")
+	ctx, cancel := context.WithTimeout(context.Background(), common.Timeout)
+	defer cancel()
+	err := common.WMIQueryWithContext(ctx, q, &dst)
+	if err != nil {
+		return ""
+	}
+	for _, v := range dst {
+		if v.Name == name {
+			return v.SerialNumber
+		}
+	}
+	return ""
+}