Introduce interfaces for difficulty & performance attributes

[minisbett]

This allows 3rd-parties using Lazer's code base to contract the attributes to ensure they always match.

This was suggested by smoogi to assist with the development of osu-native.

[minisbett]

I realized I forgot something, will get back to this tomorrow.

[minisbett]

We could change the difficulty calculator to accept the interface instead, so the structs I'm implementing in osu-native can be directly passed into the calculator. Thoughts?

Edit: Actually this does not work. Due to the nature of what I need in osu-native (and what smoogi said), I decided to not include the mods property in the interface. But since the difficulty calculator needs it it will not be satisfied.

The main issue I'm having in osu-native is that I cannot deal with a Mod[] property. If there'd be any way around it, the attributes could as well be made structs in Lazer directly.

[minisbett]

Closed in favor of #30727