Add Beta-binomial Interpolator to TTSDataset
Beta-Binomial Interpolator is taken from [DeepLearningExamples](https://github.com/NVIDIA/DeepLearningExamples/blob/master/PyTorch/SpeechSynthesis/FastPitch/fastpitch/data_function.py#L45) repository.

Signed-off-by: Oktai Tatanov <oktai.tatanov@gmail.com>