Go: implement dataset ingestion log APIs (#15421)

### What problem does this PR solve?

Part of the Python → Go API server rewrite tracked in #15240 (Dataset
ingestion section). This PR implements the three dataset ingestion
endpoints in the Go API server, mirroring the existing Python
`dataset_api_service` behaviour:

- `GET /api/v1/datasets/<dataset_id>/ingestions/summary`
- `GET /api/v1/datasets/<dataset_id>/ingestions`
- `GET /api/v1/datasets/<dataset_id>/ingestions/<log_id>`

### Type of change

- [x] Refactoring
- [x] New Feature (non-breaking change which adds functionality)

Co-authored-by: sxxtony <sxxtony@users.noreply.github.com>