[dbus] Add dbus peer tracking api. JB#41340

While mce already has functionality for tracking dbus client
details, the code was originally used for diagnostic logging
purposes and is not really usable as generic purpose peer
tracking api.

Add functions for adding/removing peer detail trackers and
make some already existing peerinfo functions available for
use outside mce-dbus module too.

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>