[AIP-94] airflowctl tasks: add clear command

[bugraoz93]

Body

Summary

Add airflowctl tasks clear

Implementation

• anything work with single endpoint under operation.py
• anything needs multiple endpoint or transformation goesn ctl/commands
• including unit and integration test under airflow-ctl-tests/

Committer

• I acknowledge that I am a maintainer/committer of the Apache Airflow project.

[henry3260]

@bugraoz93 I think we should call POST /api/v2/dags/{dag_id}/clearTaskInstances instead. I suspect the endpoint above may have a typo.

[bugraoz93]

@bugraoz93 I think we should call POST /api/v2/dags/{dag_id}/clearTaskInstances instead. I suspect the endpoint above may have a typo.

Great one Henry, thanks! Updated :)