refactor(asr-worker): save transcriptions to artifact filesystem

[ClemDoum]

Description

Addresses #10 and #9.

Note

Will require some caul updates to pass e2e test.

Changes

asr-worker

Changed

• defined transcription outputs independently of caul objects to ensure stable worker API
• refactored ASRActivities to read input data from the worker audio_root, save intermedite results in the worker workdir and save final results in the worker artifacts_dir
• update ASRResponse to return the number of transcribed files

datashare-python

Added

• add a number of utils to read/write artifact metadata as well as creating artifact directories and filesystem tree structure resilient to a large number of files

.github

Added

• activated unit and linting test for asr-worker