For review

Rework on huis:
https://pp.huismetbenen.nl/rankings/players/cognition

Doc (info about rework in the second part):
https://docs.google.com/document/d/1bp_LQpsVaX1VUL2wfIo7aoeTFPHbpBuO

The general path of Skills summing:

• Low AR + High AR -> AR
• AR + Flashlight -> FlashlightAR
• FlashlightAR + Hidden -> Cognition
• Cognition -> CappedCognition
• Aim + Speed -> Mechanical
• Mechanical + CappedCognition + Accuracy -> Total

Refactoring changes are the same for all 3 PRs.

Refactoring Difficulty Calculator changes:

• Made difficulty_multplier public
• Moved LP sum power value to the constant SUM_POWER
• Moved difficulty to performance formulas to OsuStrainSkill.DifficultyToPerformance and Flashlight.DifficultyToPerformance functions
• Changed preempt formula to use IBeatmapDifficultyInfo.InverseDifficultyRange

Refactoring Performance Calculator changes:

• Used OsuDifficultyCalculator.SUM_POWER for LP summing
• Moved difficulty to performance formulas to OsuStrainSkill.DifficultyToPerformance and Flashlight.DifficultyToPerformance functions

Osu Strain Skill changes:

• Moved Strain Decay function here
• Added DifficultyToPerformance function

Aim changes:

• Changed variables accessibility to protected to allow inheritance

Speed changes:

• Changed variables accessibility to protected to allow inheritance
• Now it's using RhythmDifficulty field instead of RhythmEvaluator class

Flashlight changes:

• Added HiddenFlashlight class to calculate FLHD regardless of active mods
• Added DifficultyToPerformance function
• Reduces multiplier to account for the fact that it's not longer LP-summed

Difficulty Calculator changes:

• Added ReadingDifficultyHighAR and HiddenFlashlightDifficulty difficulty attributes
• Included those attributes into the Star Rating calculation

Performance Calculator changes:

• Changed Flashlight performance field to the Cognition
• Added AdjustCognitionPerformance function that limits cognition performance by MechanicalPerformance + HiddenFlashlightPerformance
• Added Always use HD parameter into computeFlashlightValue that's switching between normal calculation and calculation assuming that HD is always enabled
• Added ComputePerfectFlashlightValue function to compute flashlight value with length bonus (used for capping Cognition in DifficultyCalculator)
• Removed High AR bonus
• Added ReadingDifficultyHighAR performance calculation
• Added CalculateDefaultLengthBonus function

Osu Hit Object changes:

• Added TimeFadeInRaw to account for the fact that HD changes TimeFadeIn when applied

Osu Difficulty Hit Object changes:

• Added RhythmDifficulty field to avoid calculating rhythm multiple times
• Added AnglePredictability field (self-explanatory)
• Added Preempt field
• Added FollowLineTime field to account for the fact that follow lines make high AR easier
• Added ClockRate field to adjust time-related OsuHitObject fields