Dialogue task
# What does this PR do ?

Add various functionalities to dialogue domain for NeMo

**Collection**: NLP

# Changelog 

1. Support Zero Shot Intent Recognition
2. Further refactored Dialogue module
3. Implement Dialogue GPT Generation Model 
4. Support MS Marco Data Processor
5. Implement Dialogue S2S Generation Model (HF fully supported, Megatron training supported, inference pending integration of common generation API) 
6. Support System Response Generation using user utterance and system slots based on SGD dataset
7. Support Design Data Processor
8. Implement HF BART based classifier into zero shot intent model
9. Implement Dialogue Nearest Neighbour Model
10. Refactor Dialogue SGD Data Processor to make interface with models cleaner
11. Update Nearest Neighbour Model and ZeroShotIntentModel to support SGD dataset and ZeroShot Datasets
12. Support Mellon QA Data Processor
13. Add Documentation and Tutorial

See details in [NVIDIA only dev log](https://docs.google.com/document/d/1IUerv_PLPLgzm5rLEgvHITz_RmK4cKdJKJCV7BXTJ9c/edit?usp=sharing)

# Usage
* You can potentially add a usage example below

```python
# Add a code snippet demonstrating how to use this 
```

# Before your PR is "Ready for review"
**Pre checks**:
- [x] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [x] Did you write any new necessary tests?
- [x] Did you add or update any necessary documentation?
- [ ] Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  - [ ] Reviewer: Does the PR have correct import guards for all optional libraries?
  
**PR Type**:
- [x] New Feature
- [ ] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?

Anyone in the community is free to review the PR once the checks have passed. 
[Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md) contains specific people who can review PRs to various areas.

# Additional Information
* Related to # (issue)
