Use database abstraction for all DynamoDB calls

The ingestor is currently making [direct calls to DynamoDB](https://github.com/developmentseed/cdk-pgstac/blob/main/lib/ingestor-api/runtime/src/ingestor.py#L42) and should be updated to leverage the [services module](https://github.com/developmentseed/cdk-pgstac/blob/main/lib/ingestor-api/runtime/src/services.py).

Moved from https://github.com/developmentseed/eoapi-cdk/issues/27 for tracking.

Start by reading lib/ingestor-api/runtime/src/ingestor.py around the direct DynamoDB calls and compare them with the services module in lib/ingestor-api/runtime/src/services.py. Update the ingestor so all DynamoDB access goes through that module, then verify that no direct calls remain in the ingestor.

Written by the indexing model from the issue text.