Differentiate between 'write ring' and 'read ring' buffers

[jaynel]

Ring buffers are great for concurrent writers because they have a natural cap on memory used and overwrite the oldest entries automatically.

Ring buffers for readers can also be great for tasks like load-balancing in a round-robin fashion by just continuously reading the next element and allowing wraparound on reads.

The current implementation deletes entries from LIFO / FIFO buffers when they are read, but not from RING buffers, but it only allows Write wraparound on RING buffers. A Read wraparound RING type needs to be introduced.