Expose unsafe functions and fix process unacks

Add unsafePeekAllShards() and unsafePopAllShards() functions

This patch exposes 2 new APIs that allow the calling application to
peek into and pop from all shards of the queue.

The APIs are prepended with unsafe* because if multiple client app
instances call these APIs concurrently, it's possible that duplicate
items may be returned to the application across client instances. Hence,
these APIs must not be used unless the calling application's use case
is okay with handling duplicate items.

The DynoQueueDemo is updated to use these new APIs.

Additionally, a lot of the code is refactored in V1.