Add a ByteStream service which supports LogStream resources
Description
This MR adds a prototype ByteStream servicer for handling LogStream-related streams. This ByteStream is configured automatically by the LogStream service. Currently it won't work if deployed in the same process as a CAS, as the two ByteStream servicers are mutually exclusive.
It also adds an in-memory log stream storage implementation. This stores the streams that are in progress and handles cleaning up of streams that are finished with by keeping track of the number of readers for each stream. It also provides a simple API for the LogStream's ByteStream instance to use for writing to and reading from streams.
Issues addressed
Closes #298 (closed) and #296 (closed)