DolphinQt/HacksWidget: Convert accuracy slider to ConfigSlider

[AdmiralCurtiss]

See #13234 (comment)

We have to extend the ConfigSlider class a little bit for this use case, but it's pretty straightforward.

Less code and makes it work with the per-game config system. Seems like the obvious way to go to me?

[TryTwo]

Thanks! This is all I needed, I just couldn't think of how to code it well.

[TryTwo]

I did a quick test and it works. Properly enables/disables. Works with both game and normal gfx windows. Correct values are written and all that.

Only note I see about the code is that I think there's a general preference for optional.value()[i] over (*optional)[i].

[AdmiralCurtiss]

Only note I see about the code is that I think there's a general preference for optional.value()[i] over (*optional)[i].

Those two are different use cases. x.value() throws if there is no value, *x is UB if there is no value. Or in other words, *x is if you have already checked if there is a value, and x.value() is if you have not checked.

Anyway, I realized this doesn't even need to be optional, since we can just use an empty vector for the standard identity mapping case.

[TryTwo]

Tested again. It works. I didn't notice any issues in the code.