[tests] refactor a* pipeline tests. (#14622)

* refactor a* pipeline tests.

* [tests] fix expected slice in the sparsectrl dict/tuple test

The `test_dict_tuple_outputs_equivalent` override ported in e10f8d08e carried a
nine-value expected slice that is not the one the pre-migration file used, so CI
failed on CPU with `Shape mismatch: actual torch.Size([6]) vs expected
torch.Size([9])`.

Six is correct: the base test slices `output_tuple[0, -3:, -3:, -1, -1]` and this
pipeline's dummy inputs use `num_frames=2`, so the frame axis yields 2 rather
than 3. Restored the original values, unchanged since #14120.

The literal is only read when `torch_device == "cpu"`, which is why local GPU
runs did not catch it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>