Fixed orientation when opening YCbCr TIFF images

[radarhere]

Resolves #8554

When a TIFF image is YCbCr, Pillow calls libtiff's TIFFRGBAImageBegin

Pillow/src/libImaging/TiffDecode.c

Line 729 in 5bff2f3

readAsRGBA = photometric == PHOTOMETRIC_YCBCR;

Pillow/src/libImaging/TiffDecode.c

Lines 739 to 740 in 5bff2f3

	if (readAsRGBA) {
	_decodeAsRGBA(im, state, tiff);

Pillow/src/libImaging/TiffDecode.c

Line 295 in 5bff2f3

if (!(TIFFRGBAImageOK(tiff, emsg) && TIFFRGBAImageBegin(&img, tiff, 0, emsg))) {

Looking at that libtiff code, it then calls either PickContigCase or PickSeparateCase. Those set img->get to gtTileContig, gtStripContig, gtTileSeparate or gtStripSeparate. All four of those functions apply orientation to the image based on img->orientation.

Pillow expects to manage image orientation itself. This PR sets img.orientation to prevent libtiff from doing so.