State management

[badvision]

As a user I would like to save the emulator's current state, load it again, also have a quick-save/quick-load shortcuts. Also, it would be nifty to have rewind and fast-forward support.

[badvision]

A lot of the emulator's management of singleton objects and other object references (especially memory) were a major obstacle of getting this feature working. These have since been refactored/overhauled, but the state management feature itself is still untested in its present form. I need to re-think how I implemented state capture to make sure it's not too aggressive in a way that will impact performance. Metacheat, for example, demonstrates there is a clear limit to how crazy you can/should get. Anyway, it's still pending but I didn't obliterate the state management code when I refactored and switched to Java 17