feat(anta): Enable asyncio DEBUGs when ANTA_DEBUG is true

[gmuloc]

Description

When ANTA_DEBUG is set, set the env variable recommended in Python doc

Fixes #663

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have run pre-commit for code linting and typing (pre-commit run)
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes (tox -e testenv)

[carl-baillargeon]

LGTM. Tested locally