Add basic difficulty & performance calculation for Autopilot mod on osu! ruleset

[tsunyoku]

This PR adds a base for difficulty & performance calculation for the Autopilot mod.

These are the changes:

• The speed skill will not consider note distance when Autopilot is enabled.
• Speed difficulty is reduced (50%) to account for speed including more than just tapping skill and the assumed added hand availability.
• Flashlight difficulty is reduced by 60%.
• Aim difficulty & performance are completely removed.
• Approach rate bonuses in speed performance calculation are completely removed.

[stanriders]

#20693 (comment)

Apart from that, speed should probably be reduced by at least 50% since you can use two hands for tapping

[tsunyoku]

#20693 (comment)

Apart from that, speed should probably be reduced by at least 50% since you can use two hands for tapping

For the comment you linked, I feel that... I noticed this same thing when I add diffcalc for anyh mod.

As for reducing by 50% - unsure. I did some testing with this system before PRing and I think if we reduce by even 50% values will be worth very low overall. And 2 hands? What benefit does this have? It's still 2 keys. I think I can understand reducing it more, but that drastically and for that reason, unsure if I agree.

[stanriders]

Using 2 hands is quite a lot easier since you can use the whole hand for tapping, as well as switching fingers at any time. 50% might be a bit too big, but if you consider that speed also has distance scaling it sounds okay to me

[tsunyoku]

Using 2 hands is quite a lot easier since you can use the whole hand for tapping, as well as switching fingers at any time. 50% might be a bit too big, but if you consider that speed also has distance scaling it sounds okay to me

I set distance to 0 on speed for this reason (see https://github.com/ppy/osu/pull/21211/files#diff-63100aca8fa85bf402677740e45b3fc1ab11c505357c859740bf591b35cacf98R68). Still an issue?