USB device disconnection is detected via a hotplug callback when it is
supported.
In addition, report disconnection on libusb calls returning
LIBUSB_ERROR_NO_DEVICE or LIBUSB_ERROR_NOT_FOUND. This allows to detect
disconnection after a libusb call when hotplug is not available.
PR #3011 <https://github.com/Genymobile/scrcpy/pull/3011>
Acksync is used to delay HID events until some request (in practice,
device clipboard synchronization) is acknowledged by the device.
This mechanism will not be necessary for OTG mode.
PR #2974 <https://github.com/Genymobile/scrcpy/pull/2974>