A regression from the property cache refactor caused properties like
Gio.NetworkMonitor.network_available to disappear. This was because
NetworkMonitor is an interface, implemented by a non-introspectable
class, i.e. Gio.NetworkMonitor.get_default() gives you an instance of
GNetworkMonitorBase which does not have introspection information.

To fix this, we iterate through all the interfaces implemented by a
non-introspectable type, and check if the ID to be resolved is a property
of one of them, and define it on the prototype if so. For this we factor
out some code into separate functions, and change resolve_no_info() to
have a parameter specifying whether to consider only methods or both
methods and properties.

Closes: #182