Add yt-queue-api user for registration manager

[ItIsApachee]

Currently, all proxies read consumer registrations under root user.
Since sys tablet cell bundle is used for queue agent state tables, it would be better to use a separate user here.
@savnadya proposed yt-queue-api name for such user, as it is the user used to implement internals of queue api, and it seems like the perfect choice here.
Besides that, //sys/@cluster_connection/queue_agent/queue_consumer_registration_manager/user should be set to yt-queue-api.

As for the permissions of the user, it seems like the best choice would be to only grant read and write access to required tables (or the whole directory).