[debugger] TelepathyProcess extracted from DebugMessageView

The main goal of this change is to split logic and UI parts

This is the first step in direction to debugger, which:
1) works with any Telepathy process with DebugInterface support;
2) detects new processess "on fly";
3) has no hardcoded services;
4) shows every single process just once, independently of a number
   dbus services, registered by the process.

The change also opens a way to QML-based UI

REVIEW: 128847