This change adds the missing transport-side support for sending HCI ISO Data packets
over the default Bulk Out endpoint when Isochronous endpoints are not enabled.
- Handles HCI_ISO_DATA_PACKET (0x05) in both `usb` and `pyusb` transports.
- Adds unit tests to verify the routing behavior.
TAG=agy
CONV=5502c76b-b272-4e43-a0b9-425a23cf137e
Josh Wu