Simplify internal logic

[Gummibeer]

The current code is relatively complex and in turn doesn't allow all TTL values the underlying Cache::remember() accepts.
This should be changed so the packages trait is primary/only responsible to automatically create the cache key, add the alias methods remember() ... to the model itself and pass everything else to the cache method and let it validate them.

As we are pre-v1 the changes can be breaking (like removing type-hints).