Add DifficultyCalculationUtils

[stanriders]

This refactors some common confusion points (strain to bpm conversions, circle-size-based distances) and adds a common sigmoid implementation. Sigmoid curves were kept the same which resulted in some unusual exponents like ex-2e, but values shouldn't change at all (from my limited testing they did not)

[tsunyoku]

Approving based on code/concept. @smoogipoo sheets to verify no changes?

[smoogipoo]

!diffcalc
RULESET=osu

[smoogipoo]

!diffcalc
RULESET=taiko

[smoogipoo]

!diffcalc
RULESET=mania

[github-actions]

Target: #30536
Spreadsheet: https://docs.google.com/spreadsheets/d/1yx1fERXXk6HbhCzwVseuyTSUGlXVOP13AHmfEwL2Ke0/edit

[github-actions]

Target: #30536
Spreadsheet: https://docs.google.com/spreadsheets/d/1FygbTmScsmIN2QauYU7j7tm_IHnHp4ZepEa_1BUOps8/edit

[github-actions]

Difficulty calculation failed: https://github.com/ppy/osu/actions/runs/11772319963

[github-actions]

Target: #30536
Spreadsheet: https://docs.google.com/spreadsheets/d/1_SVR94QivM-b6QDcN2BaqjmrJsHgtIlGhlQsm2vU-Lw/edit

[smoogipoo]

Seems okay. I suppose the osu! pp losses are expected from the refactoring (@stanriders)?

https://docs.google.com/spreadsheets/d/1yx1fERXXk6HbhCzwVseuyTSUGlXVOP13AHmfEwL2Ke0/edit

[stanriders]

Seems okay. I suppose the osu! pp losses are expected from the refactoring (@stanriders)?

https://docs.google.com/spreadsheets/d/1yx1fERXXk6HbhCzwVseuyTSUGlXVOP13AHmfEwL2Ke0/edit

I'm not really sure what those are - all changes osu-side are in the diffcalc, but SR didn't change for any map and pp changed only for 3 pretty generic maps. It's probably some rounding errors from the sigmoid changes though, so I'd say its a non-issue

It is weird though how all of those are pretty much exactly -0.1 pp regardless of difficulty, maybe something in the sheet processing writing numbers in a weird way?

[smoogipoo]

+/- 0.1 is the minimum for changes to be added to the sheet for PP and SR, +/- 0 for score.

[smoogipoo]

lgtm