Properly re-use SimulationCache instances for auto-evo

[hhyyrylainen]

As they are meant to be reused so that reused caches in them can benefit from already being a larger size containers. This should also hopefully help with memory management as well as there wouldn't be a bunch of temporary caches that are still allocated for the entire auto-evo run thus garbage collection is slower to remove them.

[hhyyrylainen]

Probably the easiest way would be to move the caches to be managed by the auto-evo run so that it provides the cache to each step (and cleans it after each step). This way only as many caches will be needed as threads (it might even benefit from thread local memory usage to avoid locking the stack of available caches to pass to step tasks).