Text normalization takes too much time for a string which contains a lot of dates
The PR reduces number of permutations processed in [this](https://github.com/NVIDIA/NeMo/blob/a8154fd825c34de0a59309536e11ba7d5d1f94e1/nemo_text_processing/text_normalization/normalize.py#L149) loop.

1. Count number of permutations that each token gives.
2. Split sequence of tokens into smaller parts so that number of permutations from one part would not exceed certain number.
3. Verbalize every part.
4. Unite verbalizations of parts.

Closes #3450 