WS-601: Fix broken ingestion manifest builder tests and implement remaining TODOs

WS-601: Ingestion manifest builder development, part three

• don't need to create pipeline artifacts tar; it should be present in staging dir at the start
• ... but make sure we include it with ancillary image products
• implemented some pending tests
• fixed some broken tests

TODO:

• re-enable remaining disabled tests and rewrite/refactor to make them pass
• implement still-pending tests