[asr-worker]: set up logs and alerts + improve observability / debuggability

[ClemDoum]

Make it easy to trace processing by:

• logging properly and at the right level
• setting up alerts
• improving intermediary results/assets names (make it easy to find intermediate results on the filesystem based on names)

[ClemDoum]

For logs use:

• https://pypi.org/project/python-json-logger/ or https://www.structlog.org/en/stable/
• https://python.temporal.io/temporalio.workflow.LoggerAdapter.html and https://python.temporal.io/temporalio.activity.LoggerAdapter.html

[ClemDoum]

Partially addressed in #30