Fix Wi-Fi QR scanner crash problem

1. Should only set picture size from the list of supported picture sizes.
   To choose the best picture size, we should keep ratio as preview size to
   avoid image distortion and QR code scan failure.

2. When Camera#setOneShotPreviewCallback callbacks, the image data is of
   preview size, not picture size.

Bug: 132866467
Test: QrCameraTest
      manual
Change-Id: I087e5fcdf064f111e915e0872b50ca5a45ff1d26