Use Pytest with Coverage
jenkins jenkins jenkins Closed since Jenkins will be replaced with Github actions in the near future
# What does this PR do ?

- PyTest on Jenkins runs with coverage (you can see the coverage report in logs for unit tests GPU/CPU)
- Remove deprecated `pytest-runner` (plugin used earlier to run pytest via setup.py, now useless and unsupported)
- You can see now the failing/skipped/passed tests in Jenkins UI, e.g., http://10.110.40.131:8080/blue/organizations/jenkins/NeMo-multibranch/detail/PR-8250/3/tests

**Collection**: [CI]

# Changelog 
- Add specific line by line info of high level changes in this PR.

# Usage
* You can potentially add a usage example below

```shell
pytest --cov=nemo --cov-report=html test_my_awesome_feature.py
```

# Jenkins CI
To run Jenkins, a NeMo User with write access must comment `jenkins` on the PR.

# 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)
- [ ] 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

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)
