floss: dbus_propmap: Recursively call DBusArg::log to the fields

This defers to the fields' DBusArg::log if they implemented it. Before
this, even though RawAddress has a custom DBusArg::log, it won't be
called if the RawAddress is inside other structures and the default
Debug format is used.

Bug: 342337056
Tag: #floss
Test: mmm packages/modules/Bluetooth
Flag: EXEMPT, Floss-only changes
Change-Id: I97edd0236cc6bad4e162c4f02406639ca64b9a79