Groom generated YAMLs

[oesgalha]

Context

Pipelinit currently has 25 YAML templates to generate CI pipelines, bu they were built without enforcing a code format. We should make sure the templates and generated output follows the Prettier format. Also, some files use .yml and others the .yaml extension.

Finally, the generated files may contain blank lines, that we could trim:

      - run: python -m pip install pipenv; pipenv install --dev

      - run: python -m pip install pip flake8
      - run: python -m pip install pip bandit

      # Adapts Flake8 to run with the Black formatter, using the '--ignore' flag to skip incompatibilities errors
      # Reference: https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html?highlight=other%20tools#id1
      - run: pipenv run flake8 --ignore E203,E501,W503 .
      - run: pipenv run bandit -r .

Goal

• Make sure every template and generated output is formatted with the latest Prettier
• Standardize with .yaml for file extensions^1
• Remove blank lines from generated output

This could be implemented after #129 to keep it enforced