Wav2vec2.0 Script add
# What does this PR do ?

Adds a script to load Wav2Vec2.0 weights from Fair to NeMo implementation. Also adjusts NeMo implementation to be similar to Fair's.

**Collection**: [ASR]

# Changelog 
- Added script to download and load state_dict from Fairseq Wav2Vec models to NeMo equivalents
- Adjusted order of normalization operations for wav2vec preprocessing
- Changed Wav2Vec module config so that projection operation of features is done in transformer encoder
- Altered contrastive loss so config can provide option to not combine groups. (Just added an optional boolean)

# Before your PR is "Ready for review"
**Pre checks**:
- [y ] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ n] Did you write any new necessary tests?
- [ n] Did you add or update any necessary documentation?
- [ n] 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**:
- [y ] New Feature
- [ y] Bugfix
- [ ] Documentation

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


## Who can review?

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[Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md) contains specific people who can review PRs to various areas.

# Additional Information
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