Fix handling of Unicode serial numbers

Rust str are indexed by byte, so doing .take().count()
is incorrect since Unicode values are often multiple
bytes. This fixes it and adds tests for the edge
cases.

src/windows/enumerate.rs

@@ -570,4 +570,8 @@ fn test_parsing_usb_port_information() {
     assert_eq!(info.serial_number, Some("385435603432".to_string()));
     #[cfg(feature = "usbportinfo-interface")]
     assert_eq!(info.interface, None);
+
+    let unicode_serial = r"USB\VID_F055&PID_9802\3854356β03432";
+    let info = parse_usb_port_info(unicode_serial, None).unwrap();
+    assert_eq!(info.serial_number.as_deref(), Some("3854356β03432"));
 }