Allow TFBertTokenizer to use Tensorflow text BertTokenizer (and not FastBertTokenizer) to make it servable by TF Serving
### Feature request

I would like to serve a bundle of Tokenizer + Model on TF Serving, but can't do it because TF Serving still have no support for TF FastBertTokenizer annd FastBertNormalize operations (https://github.com/tensorflow/serving/issues/2064).

It would be good if we could let [TFBertTokenizer ](https://github.com/huggingface/transformers/blob/4ed0fa3676ad8900eaa982a6c5c2ad6b75c8ea46/src/transformers/models/bert/tokenization_bert_tf.py) give the user an option not to use Tensorflow FastBertTokenizer when creating a TFBertTokenizer, so that it is servable on TFServing. 

It would consist of moving (or creating an option to change) this

https://github.com/huggingface/transformers/blob/4ed0fa3676ad8900eaa982a6c5c2ad6b75c8ea46/src/transformers/models/bert/tokenization_bert_tf.py#L67-L69

To this:
```python
# to avoid naming collision with transformers BertTokenizer
from tensorflow_text import BertTokenizer as TFBertTokenizerLayer

lookup_table = tf.lookup.StaticVocabularyTable(
    tf.lookup.KeyValueTensorInitializer(
        keys=vocab_list,
        key_dtype=tf.string,
        values=tf.range(
            tf.size(vocab_list, out_type=tf.int64), dtype=tf.int64),
            value_dtype=tf.int64
        ),
        num_oov_buckets=1
)
        
self.tf_tokenizer = TFBertTokenizerLayer(
    lookup_table, token_out_type=tf.int64, lower_case=do_lower_case
)
```

### Motivation

I would like to serve a bundle of Tokenizer + Model on TF Serving, but can't do it because TF Serving still have no support for TF FastBertTokenizer annd FastBertNormalize operations (https://github.com/tensorflow/serving/issues/2064).

As this lib is much faster to solve this kind of thing than TF Serving, I thought it was worth it trying to solve it from here. 

### Your contribution

I can definitely submit a PR with that if you approve the idea. 

EDIT: I've created https://github.com/huggingface/transformers/pull/19590 to showcase the idea. 