[Decoding Bug] When the HEVC pix format is gray, the color range will error

[op200]

make a test video:

ffmpeg -i input.mkv -c:v libx265 -pix_fmt gray test.mkv

same for 10 or 12 bits gray:

ffmpeg -i input.mkv -c:v libx265 -pix_fmt gray10le test.mkv
ffmpeg -i input.mkv -c:v libx265 -pix_fmt gray12le test.mkv

use lavfilter play test video, the output color range is limited:

rbg(255,255,255) -> rbg(235,235,235)
rbg(0,0,0) -> rbg(16,16,16)

ffplay and mpv don't have this bug
lavfilter decoding AVC does not have this bug either