[POC] Try to provide a shortcut to send out IPC message

Instead of sending/receiving over socket fd or pipe, we add a shortcut
in case of running in single-process mode.

The advantages include:
 * Avoid message serialization/deserialization
 * Avoid system call to send/receive message over file descriptor

TODO:
 * Need to erase the pair for the channel which is closed or on error.
 * Need to profile the performance benifits, e.g. CPU usage.