Refactor Canary to follow schema of remaining ASR models
# What does this PR do ?

Refactor Canary to follow Archetype pattern of rest of ASR. Add Decoding Strategy to disentangle decoding with model  architecture.

**Collection**: [ASR]

# Changelog 
- Refactors model class to conform to ASR's archetype pattern
- Add Decoding strategy as a middle layer between model logits and text to allow extending decoding algorithms in the future
- Update configs to new schema

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**Pre checks**:
- [x] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ ] Did you write any new necessary tests?
- [ ] 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
