Add fade settings to traceable mod

[mk56-spn]

as discussed in #18114 , #18905 and #15963

This PR implements a hidden-esque effect for traceable.

code quality queries:

• I enclosed the fade specific code (since there;s a decently large amount to make it match the expected fades from people coming from hidden) in a region at the bottom, not sure if this is wanted or not

• I moved the applyToBeatmap override down there as well, even though its mostly at the top of mods from what i've perused, because it only does things related to that sub setting.

• not sure if I should have it apply the setting through two "main methods" as I have it right now (applyfade and applytraceable) or have all the fade stuff go into the main traceable method.

footage:

2022-08-18.19-12-10.mp4

[peppy]

I think it's cool to have this as an option, but I'd really prefer it to be implemented by allowing both hidden and traceable to be applied at once, rather than this kind of setting.

[mk56-spn]

I think it's cool to have this as an option, but I'd really prefer it to be implemented by allowing both hidden and traceable to be applied at once, rather than this kind of setting.

The result of traceable + hidden is invisible circles and approach circles, and fading sliders

My first proposal was to have hidden change upon enabling traceable so that it moves it's effects to approach circles in instead of circle piece. Bdach was vehemently against direct interaction of mods so I canned that

I considered housing this under hidden alone. But traceable felt like the better place since it's the " approach circle mod "

The last remaining option unless one of the above is allowed is incredibly messy and not functional. Which would be TC and HD not detecting eachother but HD having a subsetting which switches its effect to the approach circle. But that means the default effect is some mess where half the map ( the nonsliders ) is not visible .

So as you can see I kind of have my hands tied without being allowed to have them detect eachother. Unless I'm missing something which is perfectly plausible