* Mark pipeline tests to skip them easily

* Mark the mixin as pipeline test

* Update src/transformers/testing_utils.py

Co-authored-by: Yih-Dar <2521628+ydshieh@users.noreply.github.com>

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Co-authored-by: Yih-Dar <2521628+ydshieh@users.noreply.github.com>