Remove OneTimeCallback and provide contructor in C for interfaces

[emgre]

In C, it makes sense to still have a on_destroy callback in OneTimeCallbacks to avoid leaks. Therefore, I guess we can just delete OneTimeCallback and use Interface everywhere. Also, it would be nice to have construtor methods for interfaces.

• Remove OneTimeCallback
• In async method, check that the interface has a single callback with a single argument
• Add builder methods to C bindgen