Three-way merge of the changes EffectCraft made to its av1enc and hevcenc
crates after craft-video took them:
- hevc: EncoderConfig carries colour_primaries, transfer_characteristics and
matrix_coeffs (H.273 code points, BT.709 by default) and the VUI writes them.
- av1: EncoderConfig carries color_primaries, transfer_characteristics and
matrix_coefficients and color_config writes them.
- av1: motion search keeps a visited set and stops a SAD once it cannot win,
SATD has fixed-size kernels, and a decision snapshot saves only the block's
BlockDecoded flags. Output is unchanged.
ffprobe tests check the colour description of both streams.
