[TTS] Update Aligner, add new methods to AlignmentEncoder
Signed-off-by: Oktai Tatanov <oktai.tatanov@gmail.com>

# What does this PR do ?

**Collection**: [tts]

# Changelog 
- refactoring of Aligner code and config, replacing deprecated datasets with `TTSDataset` 
- adding three methods to AlignmentEncoder which can be useful for Neural G2P research
  
**PR Type**:
- [x] New Feature
- [ ] Bugfix
- [ ] Documentation