pixel-formats: Add NV15/20/30 YUV 10bpc formats
NV15/20/30 are a family of 10bpc YUV formats which have 4 horizontally-adjacent samples packed into a 40-bit cluster. The difference between 15/20/30 is in the subsampling.
No fallbacks are provided, as there is no format pairing which would allow us to sensibly unpack the clusters.