[camera_android_camerax] Support RGBA_8888 image format group  #151193

CameraController cameraController = CameraController(
    cameras![selectedCameraIndex],
    ResolutionPreset.medium,
    imageFormatGroup: ImageFormatGroup.rgba8888,
);
cameraController.startImageStream((CameraImage image) {
    ///Computer vision tasks with rgba8888 image format group bytes
});

  /// Initializes the camera on the device.
  ///
  /// Since initialization of a camera does not directly map as an operation to
  /// the CameraX library, this method just retrieves information about the
  /// camera and sends a [CameraInitializedEvent].
  ///
  /// [imageFormatGroup] is used to specify the image format used for image
  /// streaming, but CameraX currently only supports YUV_420_888 (supported by
  /// Flutter) and RGBA (not supported by Flutter). CameraX uses YUV_420_888
  /// by default, so [imageFormatGroup] is not used.
  @override
  Future<void> initializeCamera(
    int cameraId, {
    ImageFormatGroup imageFormatGroup = ImageFormatGroup.unknown,
  }) async {
  ...
  }