[Patch-t5-tokenizer] Patches the changes on T5 to make sure previous behaviour is still valide for beginning of words
# What does this PR do?
There was a small typo that modified the behaviour in #24565, the test were not able to catch it.  #24569
When a sentence does not start with a space, a space was added.
Before:
```python
>>>tokenizer.tokenize("Hello <extra_id_0>")
['_', '_Hello', '<extra_id_0>']
```
After:
```python 
>>>tokenizer.tokenize("Hello <extra_id_0>")
['_Hello', '<extra_id_0>']
```
# Big bug 35 models involved
Not only punctuation but anything after a special token is basically wrong... Let's ignore the fact that we also split when it's the beginning of word less important
<img width="1020" alt="image" src="https://github.com/huggingface/transformers/assets/48595927/d805bd21-4f2a-411b-ad2b-754f4f69517c">


Tests were added as they were green before merging
_The documentation is not available anymore as the PR was closed or merged._<|||||>Ran all the tests with `RUN_SLOW`, switch-ci is fixed<|||||>Until the added tokens are fixed, this will break the slow version that use extra ids, because by default we strip left and right..... So buggy <|||||>The bug has always been in T5, but since some models were trained with the bugged T5, we will let the user decide whether or not they incorparate the change