Completes the d1bc1413 cleanup pass on the five files that were
skipped because dataloader had pending modifications. With those
modifications now landed (commits 7cdbcc94 + c2a22560), the dead
code in optical_flow + the four aux-using vbench metrics
(color/multiple_objects/object_class/spatial_relationship) can go.
Mechanical removal of batch_unit class attrs and trial_forward
method overrides — neither is read anywhere since calibrate() was
deleted in 502f061d.
Parity verified on fs-mbz-gpu-085: byte-identical to v3 baseline.
shaoxiongduan
2b8e5a56a8