WS-507: Refactored to eliminate circular dependency and `__repr__()`s; tests pass.

...i/executables/pexable/ingest_envoy/ingest_envoy/ingest.py

...s/pexable/ingest_envoy/ingest_envoy/ingestion_manifest.py

...le/ingest_envoy/ingest_envoy/ingestion_manifest_writer.py

...xecutables/pexable/ingest_envoy/ingest_envoy/utilities.py

apps/cli/executables/pexable/ingest_envoy/test/conftest.py

...ables/pexable/ingest_envoy/test/test_evla_cal_manifest.py

...pexable/ingest_envoy/test/test_miscellaneous_manifests.py