Refactor: libcib,libcrmcommon: best practices for more internal IPC-related API

should have been done with c21cd58d

This includes moving some IPC-related functions from utils.c to ipc.c,
and some CIB IPC-related constants from include/crm/cib/internal.h to
include/crm_internal.h (since they are used by libcrmcommon as well as libcib).