Adding support for `pipeline("automatic-speech-recognition")`.
# What does this PR do?

Implements the default load logic to make `AutomaticSpeechRecognitionPipeline` work
like other pipelines with `pipeline(task="automatic-speech-recognition", ...)`.

The main issue with current implementation is `"config"` choice for AutoModel. It would be great to have the
possibility to have something like `AutoModelFor` that would implement
the same logic (Load the config, check Architectures and load the first
one)

Alternatives:

- Implement `AutoModelForCTC`, `AutoModelForConditionalGeneration`, allow the `ALLOWED_TASKS` mapping
  to accept iterables, and try to load models accordingly.
  This might enable better switch handling case here: https://github.com/huggingface/transformers/blob/master/src/transformers/pipelines/automatic_speech_recognition.py#L141 with actual `isinstance` instead of the dummy string check.
  This would change `ALLOWED_TASKS` logic but might be closer to existing code.


Other discussion could include the `Mixin` which wasn't used here. The main reason is because the mixin supposes
that TF is enabled, but the ASR models do not have a TF alternative right now. Still imported the main tests.

Better care of error raised could be added for the `feature_extractor` missing or incorrect.



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Fixes # (issue)


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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- [ ] Did you write any new necessary tests?


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Models:

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This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.<|||||>Ping
<|||||>@patrickvonplaten could make another review , I think the previous PR that reads `config.architectures` alleviated any issue for this PR.

what do you think ?<|||||>@sgugger

Maybe a small sanity check if you don't mind (code has significantly changed since last review) ? Should be for the better.