feat: Use DBResponse for get_run_ids and get_task_ids

[xychu]

Return more specific status code and detail msg when DB got exception.

[neksa]

this PR can possibly fix

"Traceback (most recent call last):
  File \"<frozen runpy>\", line 198, in _run_module_as_main
  File \"<frozen runpy>\", line 88, in _run_code
  File \"/root/services/metadata_service/server.py\", line 54, in <module>
    main()
  File \"/root/services/metadata_service/server.py\", line 48, in main
    loop.run_forever()
  File \"/usr/local/lib/python3.11/asyncio/base_events.py\", line 607, in run_forever
    self._run_once()
  File \"/usr/local/lib/python3.11/asyncio/base_events.py\", line 1922, in _run_once
    handle._run()
  File \"/usr/local/lib/python3.11/asyncio/events.py\", line 80, in _run
    self._context.run(self._callback, self._args)
  File \"/opt/latest/lib/python3.11/site-packages/aiohttp/web_protocol.py\", line 433, in _handle_request
    resp = await request_handler(request)
  File \"/opt/latest/lib/python3.11/site-packages/aiohttp/web_app.py\", line 504, in _handle
    resp = await handler(request)
  File \"/root/services/metadata_service/api/utils.py\", line 23, in wrapper
    db_response = await func(args, kwargs)
  File \"/root/services/metadata_service/api/utils.py\", line 63, in wrapper
    return http_500(str(err))
  File \"/root/services/metadata_service/api/utils.py\", line 43, in http_500
    traceback_str = get_traceback_str()
  File \"/root/services/metadata_service/api/utils.py\", line 61, in wrapper
    return await func(args, kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File \"/root/services/metadata_service/api/task.py\", line 194, in create_task
    run_number, run_id = await self._db.get_run_ids(flow_id, run_number)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File \"/root/services/data/postgres_async_db.py\", line 112, in get_run_ids
    return run.body['run_number'], run.body['run_id']
           ~~~~~~~~^^^^^^^^^^^^^^
           TypeError: string indices must be integers, not 'str'