Making `ConvBert Tokenizer` independent from `bert Tokenizer`
# What does this PR do?

Fixes #19303

Added `BertTokenizer` class in tokenization_convbert.py and `BertTokenizerFast` in tokenization_convbert_fast.py

_The documentation is not available anymore as the PR was closed or merged._<|||||>Done! @sgugger  do i need to do same for convbert_fast?<|||||>@sgugger Thanks for quick feeback,
For tokenization_convbert.py i have change the comment to `# Copied from transformers.models.bert.tokenization_bert.BertTokenizer with ConvBertTokenizer->BertTokenizer`

and for tokenization_convbert_fast.py i have change the comment to `# Copied from transformers.models.bert.tokenization_bert_fast.BertTokenizerFast with ConvBertTokenizerFast->ConvBertTokenizer
`

for convbert_fast `make repo-consistency` gives error : - src/transformers\models\convbert\tokenization_convbert_fast.py: copy does not match models.bert.tokenization_bert_fast.BertTokenizerFast at line 55<|||||>You'll need to add broader patterns than just the full name of the tokenizer as BERT is used in the docstrings for instance. To see what the copy utils wants to modify, you can run `make fix-copies` locally :-)<|||||>After running `make fix-copies` it changes `slow_tokenizer_class = BertTokenizer` but it should be `ConvBertTokenizer` in tokenization_convbert_fast.py<|||||>Yes, that's why I made the suggestions above.<|||||>So, do i need to copy `BertTokenizer` and `BertTokenizerFast` class to tokenization_convbert_fast.py as after adding those classes it passes all tests<|||||>Just accept the suggestions above.<|||||>Done @sgugger are there any more changes?