Move settings to `pyproject.toml`. Remove deprecated `pytest-runner`
# What does this PR do ?

- move settings from old-style `setup.cfg` to `pyproject.toml` (recommended by most of the tools)
- remove deprecated `pytest-runner` according to the [documentation](https://github.com/pytest-dev/pytest-runner#deprecation-notice)

**Collection**: [Note which collection this PR will affect]

# Changelog 
- create `pyproject.toml` with settings from `setup.cfg` for `isort` and `pytest`
- remove `setup.cfg`
- remove `pytest-runner` from `setup.py`

# Usage
It is not possible anymore to use `python setup.py test` (actually, not used in project). 

`pytest <options>` should be used for testing purpose.


# 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)
