Add benchmark for peer-to-peer dbus communication using libglib

Add benchmark for peer-to-peer dbus communication using libglib

This commit adds new set of DBus-Glib benchmarks. The difference from
previous benchmarks is that clients communicate directly
(using libglib private socket) and not through dbus-daemon.

The benchmark should allow to measure latency/throughput of
socket-based communication with dbus data format. Compared to
communication to dbus-daemon the following is not a part of
the transfer and needs to be kept in mind while comparing
performance that:

- policy is not checked
- only 1-to-1 communication is allowed (no broadcasts).

Change-Id: I84d090a0f3e0d70f3ceb20de36dac41e19e38ae7