Add mania hidden/fadein combo scaling coverage

[Mogiiii]

• closes osu!mania hidden mod does not factor in current combo #22355

Adds dynamic coverage for mania hidden/fadein mod which increases with combo. Enabled by default.

Default hidden coverage has been reduced so that default settings are closer to osu!stable gameplay.

Specific tuning of coverage and combo_to_reach_max_coverage will need mania community feedback since mania and hidden are things I am not great at.

[bdach]

Initial review. Only focusing on structure for now, haven't even looked as to whether any of the coverage numbers and formulae are anywhere close to correct.

[Mogiiii]

This should now match stable when lazer coverage setting matches stable's minimum coverage, and lazer's max coverage is equal to the max coverage possible to reach on stable. To do that we will need to reduce hidden max coverage to whatever stable's is (I need to measure it still). I feel like reducing the range that you can set coverage makes the coverage mod setting less impactful, but I also think trying to hardcode arbitrary values for dynamic coverage seprate from what already exists is a bad design.

another concern, the rate at which the civerage changes scales with the coverage setting. I feel like this makes the most sense, but I'd like a second opinion on if that is a valid direction. an alternative would be to scale linearly with combo (I.E. +1 combo is always +X% of the playfield, regardless of any setting)

I have also entirely ingored designing how mod score multipliers should work with this since it was out of scope. However, there was the recent meeting discussing gameplay balance, so I am unsure if I now need to also include some plan for that.

[bdach]

To do that we will need to reduce hidden max coverage to whatever stable's is (I need to measure it still). I feel like reducing the range that you can set coverage makes the coverage mod setting less impactful, but I also think trying to hardcode arbitrary values for dynamic coverage seprate from what already exists is a bad design.

You could have two settings for initial and maximum coverage, similarly like the time ramp mods have an initial and final playback rate.

another concern, the rate at which the coverage changes scales with the coverage setting. I feel like this makes the most sense, but I'd like a second opinion on if that is a valid direction

I think this makes sense also (and can tie nicely into the proposal above).

I have also entirely ingored designing how mod score multipliers should work with this since it was out of scope

It is out of scope still. We probably need a holistic balance pass anyhow.