More type cleanups

SPA_ID_* -> SPA_TYPE_*. We use 'type' for all registered types.
ID refers to either a registered type or an enum.
Improve introspection of object ids. Make 0 an invalid enum and
use it to look up the object id type.
Move some type-info files together.
Swap type and id of the object, we first specify the type and then
the id because the meaning of the id depends on the object type.

src/modules/module-client-node.c

@@ -125,7 +125,7 @@ static int module_init(struct pw_module *module, struct pw_properties *propertie
 
 	factory = pw_factory_new(core,
 				 "client-node",
-				 PW_ID_INTERFACE_ClientNode,
+				 PW_TYPE_INTERFACE_ClientNode,
 				 PW_VERSION_CLIENT_NODE,
 				 NULL,
 				 sizeof(*data));