utils: Add interceptor and injector for IPC PubSub messages

utils: Add interceptor and injector for IPC PubSub messages

Because the IPC module uses the file system to exchange messages,
remote systems cannot communicate without a shared file system such
as NFS. However, NFS may not be an option due to resource and
security constraints.

This commit adds the ipc-tap and ipc-inject utilities, which can be
used to bridge messages over an SSH connection. As the name suggests,
the ipc-tap utility taps into topics and outputs messages published
on those topics to standard output.
The ipc-inject reads messages from standard input and injects them
into local PubSub topics.