Same issue between dvd.rom and drool.rom

I think there are 2 things that could happen when loading a rom:

• Create a new emulator every time (which will also create new devices). However, the devices could rely on other external state (e.g. the DOM) which needs to be reset anyway.
• Provide a reset() on the emulator, the core, and the devices, where everyone resets their own state. This is going to be more efficient, but maybe slightly more work.

I just realized that the JS core resets state in load(). Makes sense, I need to do that as well in the wasm core.