Introduce infrastructure necessary to support receiving, sending and replying (to) Bluetooth authentication/pairing requests:
- During startup, the Bluetooth driver now creates a "pairing agent" and registers it with BlueZ. The pairing agent is a DBus object implementing the `org.bluez.Agent1` interface (documented [here](https://github.com/bluez/bluez/blob/master/doc/org.bluez.Agent.rst)), which receives authentication requests from BlueZ. The pairing agent then forwards the request data to the PE driver, in form of a `WINEBLUETOOTH_EVENT_AUTH_EVENT` event. The agent is unregistered during driver shutdown. - Right now, the agent only supports Numeric Comparison pairing requests.
- Create a new auxiliary device, `??\WINEBTHAUTH` during driver startup. This device handles authentication functionality that is independent of radio PDOs on the system, which allows the userspace APIs to not track individual Bluetooth radio objects to implement authentication. `WINEBTHAUTH` right now serves two purposes: - Serve as the device object for which `GUID_WINEBTH_AUTHENTICATION_REQUEST` PnP events are broadcasted. This event is sent whenever the Bluetooth event loop in (`bluetooth_event_loop_thread_proc`) receives `WINEBLUETOOTH_EVENT_AUTH_EVENT`. The event's buffer contains a `struct winebth_authentication_request` value, which contains data relevant to the incoming auth request. - Handle the `IOCTL_WINEBTH_AUTH_REGISTER` IOCTL. This simply calls the [`RequestDefaultAgent` BlueZ method](https://github.com/bluez/bluez/blob/master/doc/org.bluez.AgentManager.rst#vo...) right now, which asks BlueZ to send all incoming Bluetooth authentication requests to Wine's pairing agent (described above). This is not always strictly necessary, but is useful if there already is a default pairing agent set. - `WINEBTHAUTH` will also ultimately be in charge of responding to authentication requests, which I'll be adding in the next-ish MR(s).
- Implement `BluetoothRegisterForAuthenticationEx` and `BluetoothUnregisterAuthentication`. Registration is done by invoking `IOCTL_WINEBTH_AUTH_REGISTER`, and then listening for `GUID_WINEBTH_AUTHENTICATION_REQUEST` events on a `HANDLE` to `??\WINEBTHAUTH` using the newly added `CM_Register_Notifications`.
To keep the MR from getting any larger, I have not included support for `BluetoothSendAuthenticationResponseEx`. That will likely be introduced in the future.
-- v5: bluetoothapis/tests: Add tests for BluetoothRegisterForAuthenticationEx and BluetoothUnregisterAuthentication.