Add meaningful Spigot Timings

[Christoph]

It is often the case, that we want to measure performance using spigot timings. https://timings.spigotmc.org/

However, coroutines schedules using plugin.launch {} often yield a name like CancellableContinuationImpl(Single) which is not helpful if we are using many coroutines spread across larger plugins. It should be possible to use class names in the same way as the standard bukkit scheduler.