Less transforms in gameplay is always better.
This fixes repeat arrows animating completely incorrectly in the editor
(and probably gameplay when rewinding).
They had scale transforms applied to them in two places: the actual
legacy pieces themselves (esp. `LegacyHitCirclePiece`), and on the
`DrawableSliderRepeat` level.
This change moves all of the scale transforms to the skinnable pieces.
Argon and triangles have received a copy of the previous logic each,
so behaviour on those skins should not change.
