Added module for storing variable length packets in a ring buffer.
Implementation assumes multiple producing contexts and single consumer.
API provides zero copy functionality with alloc, commit, claim, free
scheme.
Additionally, there are functions optimized for storing single word
packets and packets consisting of a word and a pointer. Buffer can work
in two modes: saturation or overwriting the oldest packets when buffer
has no space to allocate for a new buffer.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
