 The `convert_tokens_to_string` method fails when the added tokens include a space
## Environment info
```
- `transformers` version: 4.17.0
- Platform: Linux-5.4.144+-x86_64-with-Ubuntu-18.04-bionic
- Python version: 3.7.12
- PyTorch version (GPU?): 1.10.0+cu111 (False)
- Tensorflow version (GPU?): 2.8.0 (False)
- Flax version (CPU?/GPU?/TPU?): not installed (NA)
- Jax version: not installed
- JaxLib version: not installed
```

## Information

The bug that was identified [for the decode method regarding added tokens with space ](https://github.com/huggingface/transformers/issues/1133)also occurs with the `convert_tokens_to_string` method.

## To reproduce

```python
from transformers import AutoTokenizer, AddedToken

def print_tokenizer_result(text, tokenizer):
    text = tokenizer.convert_tokens_to_string(tokenizer.tokenize(text))
    print(f"convert_tokens_to_string method: {text}")

model_name = "patrickvonplaten/norwegian-roberta-base"

tokenizer_init = AutoTokenizer.from_pretrained(model_name)
tokenizer_init.save_pretrained("local_tokenizer")

model_name = "local_tokenizer"
tokenizer_s = AutoTokenizer.from_pretrained(model_name, use_fast=False)
tokenizer_f = AutoTokenizer.from_pretrained(model_name, use_fast=True)

new_token = "token with space"
tokenizer_s.add_tokens(AddedToken(new_token, lstrip=True))
tokenizer_f.add_tokens(AddedToken(new_token, lstrip=True))

text = "Example with token with space"
print("Output for the fast:")
print_tokenizer_result(text, tokenizer_f)
print("\nOutput for the slow:")
print_tokenizer_result(text, tokenizer_s)
```

## Expected behavior

No error or the fact that `convert_tokens_to_string` is a private method.

One way to solve this problem is to move the logic implemented in the `_decode` method into the `convert_tokens_to_string` method. 
https://github.com/huggingface/transformers/blob/9d88be57785dccfb1ce104a1226552cd216b726e/src/transformers/tokenization_utils.py#L933-L946

The only issue will be that we'll need to add new argument (`skip_special_tokens`, `clean_up_tokenization_spaces`, `spaces_between_special_tokens`) to the `convert_tokens_to_string` method of the slow tokenizers.

Another option is to make the method `convert_tokens_to_string`  private.
<|||||>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/main/CONTRIBUTING.md) are likely to be ignored.