Upgrade the libtiffpic test harness from decode-only smoke tests to
full output verification using CRC32 reference hashes. 50 of 61 images
now have hash-verified decoded output; the remaining 11 use unsupported
formats (YCbCr subsampling, Fax3, etc.) and remain as decode-only tests.
Uses read_image_to_buffer (the non-deprecated API) with ByteOrder::convert
for cross-platform LE normalization.
Remove the 13 individual depth tests from decode_images.rs — they tested
the same libtiffpic flower images that are now hash-verified here.
Lilith River
83dbb750df