Strange implementation of `convert_tokens_to_string` in albert tokenizer.
Hi,

the albert tokenizer implements the `convert_tokens_to_string` function:

https://github.com/huggingface/transformers/blob/ba0d50f2148f0db0e04a80cddb1f57ce0c91c182/src/transformers/models/albert/tokenization_albert.py#L222-L223

While the deberta v2 and some other tokenizer just delegate this to the sentencepiece tokenizer:

https://github.com/huggingface/transformers/blob/ba0d50f2148f0db0e04a80cddb1f57ce0c91c182/src/transformers/models/deberta_v2/tokenization_deberta_v2.py#L146

IMO it would be better to always delegate to the sentencepiece tokenizer. What do you think?

## PS:
Some more examples here 

https://github.com/huggingface/transformers/blob/ba0d50f2148f0db0e04a80cddb1f57ce0c91c182/src/transformers/models/barthez/tokenization_barthez.py#L251-L252

https://github.com/huggingface/transformers/blob/ba0d50f2148f0db0e04a80cddb1f57ce0c91c182/src/transformers/models/camembert/tokenization_camembert.py#L251-L252

https://github.com/huggingface/transformers/blob/ba0d50f2148f0db0e04a80cddb1f57ce0c91c182/src/transformers/models/m2m_100/tokenization_m2m_100.py#L187-L188

https://github.com/huggingface/transformers/blob/ba0d50f2148f0db0e04a80cddb1f57ce0c91c182/src/transformers/models/mbart/tokenization_mbart50.py#L208-L209

https://github.com/huggingface/transformers/blob/ba0d50f2148f0db0e04a80cddb1f57ce0c91c182/src/transformers/models/speech_to_text/tokenization_speech_to_text.py#L169-L173

https://github.com/huggingface/transformers/blob/ba0d50f2148f0db0e04a80cddb1f57ce0c91c182/src/transformers/models/xlm_prophetnet/tokenization_xlm_prophetnet.py#L264-L265
Indeed, you're probably right! When updating the ALBERT tokenizer to use the `sentencepiece.decode` instead of the manual handling - do all tests pass? Even the integration test?

Makes me think we really should have integration tests for all tokenizers, as scenarios like this one are bound to happen.<|||||>Well yes. While "adding subword regularization in more tokenizers": #11417
I recognized that the tokenizers could benefit from some bigger refactoring.
Pulling commen functions into a base class would be nice. And while doing this adding tests....
There is  lot of duplicate code there...

I might do this as a PR the next days (weeks) - we will see.<|||||>PR with a fix started: #11716<|||||>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.<|||||>I am still working on this...<|||||>Fixed in #11716 closing here.