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.
Param ids and IO ids are now simple enums.
Move some type info in one place, delete some type-info files
Fix type debug
Make audio layout an enum
Mark more enums as enums in types so they show us with their names in
the debug.
