usb-ids: className/interfaceName helpers; readable device classes in the bus log

The logs read 'class 9/0/0' where they could say 'Hub'. usb-ids gains
className (a device/interface class byte -> 'Hub', 'HID', 'Mass Storage',
...) and interfaceName (a HID boot interface -> 'HID boot keyboard' /
'HID boot mouse'), both host-tested with usb-ids. The bus driver's
enumerate + register lines now read, e.g.:

  port 21 device: Hub vendor 0x05e3 product 0x0626, 1 interface(s)
  port 21 interface 0: Hub (9/0/0) registered as device 47
  port 5 interface 0: HID boot keyboard (3/1/1) registered as device 32

so a real-hardware log is scannable by eye. Full USB case set green
(hub regexes follow the new 'device: <name>' format).

test/qemu_test.py

@@ -494,7 +494,7 @@ CASES = [
      # B4a: the hub powers its ports. B4b: the keyboard behind it enumerates
      # (route string + TT) and binds usb-hid-keyboard.
      "expect": r"(?s)(?=.*hub slot \d+: \d+ downstream ports powered)"
-               r"(?=.*hub slot \d+ port \d+ device vendor 0x0627)"
+               r"(?=.*hub slot \d+ port \d+ device:.*vendor 0x0627)"
                r"(?=.*usb-hid-keyboard: ok \(device 3)",
      "fail":   r"DANOS-TEST-RESULT: FAIL"},
     # USB mass storage end to end: the boot usb-storage device (the FAT32 image,
@@ -676,7 +676,7 @@ CASES = [
                     "-device", "usb-hub,bus=xhci2.0,port=1",
                     "-device", "usb-hub,bus=xhci2.0,port=1.1",
                     "-device", "usb-kbd,bus=xhci2.0,port=1.1.1"],
-     "expect": r"(?s)(?=.*hub slot \d+ port \d+ device vendor 0x0409)"
+     "expect": r"(?s)(?=.*hub slot \d+ port \d+ device:.*vendor 0x0409)"
                r"(?=.*usb-hid-keyboard: ok \(device 3)",
      "fail":   r"DANOS-TEST-RESULT: FAIL"},
     # Hub-downstream disconnect (B4c): device_del the keyboard behind the hub;