Introduce `batch-fetch` REST API Endpoint Similar to the `batch-apply-object` endpoint, there are the same benefits if we batch the refs into one fetch call. Whether to use the batching endpoint is configurable (false by default) with the existing behaviour preserved for backwards compatibility. Bug: Issue 40015567 Change-Id: Idb83e5cfcc4e8aae33c28f906518cad56ae9fc13