Change some small classes to struct to avoid potential null check.
Change some small classes to struct to avoid potential null check.

ppy/osu,EVAST9919/osu,UselessToucan/osu,peppy/osu-new,NeoAdonis/osu,naoey/osu,naoey/osu,ppy/osu,peppy/osu,smoogipoo/osu,UselessToucan/osu,Frontear/osuKyzer,johnneijzen/osu,naoey/osu,ZLima12/osu,UselessToucan/osu,Drezi126/osu,peppy/osu,ZLima12/osu,DrabWeb/osu,smoogipoo/osu,johnneijzen/osu,2yangk23/osu,peppy/osu,DrabWeb/osu,DrabWeb/osu,NeoAdonis/osu,smoogipoo/osu,Damnae/osu,ppy/osu,EVAST9919/osu,Nabile-Rahmani/osu,smoogipooo/osu,NeoAdonis/osu,2yangk23/osu