Set task and language tokens for whisper model
### Feature request

Hi @ArthurZucker, thanks for the great work on whisper models.

I would like to know if it's possible to also have a `set_prefix_tokens` function in `WhisperForConditionalGeneration`, which receives the language/task name and changes the language/task token in `model.config.forced_decoder_ids`, in order to run the ASR inference on languages other than EN. 

As far as I know it has by default `['<|en|>', '<|transcribe|>', '<|notimestamps|>']`, so I have to get the language token ID first and set it manually before running generate



### Motivation

An easy API to set language/task would be useful.

### Your contribution

Willing to do if this function doesn't exist
Hey! That's a good idea and also on my TODO! 
It is debatable whether we should have this in the `WhisperForConditionalGeneration` or add a new class for multilingual Decoding which would do this automatically. We could also add a `WhisperForSequenceClassification` class which would just detect the language. 

CC @sgugger and @patrickvonplaten as this is really a design question. <|||||>I think this is something we would want to solve with generate use-case specific configurations (cc @gante) <|||||>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.

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