Ring buffer data structures

[harendra-kumar]

Make ring buffer a first class streaming citizen by providing read unfold and write fold for it just like array. That will enable us to use ringbuffers more e.g. lastN can actually return a ringbuffer instead of array.

[harendra-kumar]

PR #1340 added signatures for the ring buffer APIs. Let's implement those.

[adithyaov]

This will also require extensive testing.