The new test scene is essentially a copy of TestSceneHoldNoteInput, modified to test the judgement changes applied by the new mod. A base class might need to be abstracted out for them.
Covers the scenarios mentioned in #21371. Turns out this seems mostly okay already, so there are no fixes applied here.
BaseDifficulty
Difficulty
EffectControlPoint
Not sure why this was checking visibility. If it needs to be tested, it does not belong in an "Input" test.
Also fix null reference in Playfield