Move batch read logic into StorageABC
Description
Support for BatchReadBlobs
was introduced in !141 (merged). However, it was implemented by calling get_blob
in a loop over the input digests at the server instance level.
This MR moves that logic down into the storage level, since certain storage types might be able to implement this more efficiently than by calling get_blob
in a loop.
Edited by Rohit Kothur