Fixing batching pipelines on single items for ChunkPipeline (#21132)
* Fixing #20783
* Update src/transformers/pipelines/base.py
* Fixing some tests.
* Fixup.
* Remove ffmpeg dep + a bit more relaxed for bigbird QA precision.
* Better dataset.
* Prevent failing on TF.
* Better condition. We can't use `can_use_iterator` since we cannot use it
directly.