Circular buffer (enhanced)

This variant of a circular buffer uses static allocation.

This buffer is not meant for producer-consumer synchronization, it's geared towards use cases where the buffer is accessed from a single thread, such as to keep a running average.

The full capacity is utilized thanks to internally storing its length. The buffer has both front and back sets of push/pop/peek functions, as well as a way to iterate and mutate its elements.

See the header for usage details.