Support storing intermediate results in object store

[venkat1109]

Today, cadence cannot support use-cases where intermediary steps can generate large amounts of data as results. The scaling limitation for this is the size of the history. One idea would be for the client to upload the intermediate results in an object store (ex-S3) and just use the url in the history. This task is to track support for this feature.

[ibarrajo]

At Uber we do support a simple object storage that serializes large blobs of data that could bloat the workflow history. The implementation is specific to Uber's technologies.

The implementation is trivial, similar to storing data in S3 or MongoDB. We welcome contributors to interested in implementing this!