Remove SVT_AV1_PRED_LOW_DELAY_P
The SVT_AV1_PRED_LOW_DELAY_P
prediction structure is unnecessary and should be removed (the prediction structure is already marked as invalid and inactive by comments in the code). SVT_AV1_PRED_LOW_DELAY_B
should become SVT_AV1_PRED_LOW_DELAY
and handle P and B frames (if they are both still necessary). SVT_AV1_PRED_LOW_DELAY_P
seems to be only used for incomplete MGs in random access mode, and could be easily replaced by SVT_AV1_PRED_LOW_DELAY
frames.