AV12 should be right after A420 because it is the same format with just
one plane less, instead of being next to I420/NV12 which don't have an
alpha channel.

RGBP should be before GBR because it's the same format except for the
more canonical component order.

See gstreamer-rs!790
which actually checks on the CI if the algorithm defined in
video-format.h is implemented correctly.

Part-of: <!1189>