De-duplicate a batch of two-player-related code

[twopointzero]

Can you write a one-sentence description of your request? Most two-member texture arrays (and/or usages of TJAPlayer3.stage演奏ドラム画面.bDoublePlay and similar) have associated code duplication that can be trivially eliminated in advance of a larger restructure toward treating each player's UI as a logical unit.