Add debounce to WorkingBeatmap creation at song select.
Add debounce to WorkingBeatmap creation at song select.

Improves perceived performance when quickly moving through carousel.
peppy/osu,tacchinotacchi/osu,EVAST9919/osu,smoogipoo/osu,naoey/osu,UselessToucan/osu,peppy/osu,Drezi126/osu,johnneijzen/osu,RedNesto/osu,DrabWeb/osu,Nabile-Rahmani/osu,ppy/osu,ZLima12/osu,ppy/osu,peppy/osu-new,naoey/osu,johnneijzen/osu,naoey/osu,ZLima12/osu,Frontear/osuKyzer,NeoAdonis/osu,UselessToucan/osu,peppy/osu,UselessToucan/osu,NeoAdonis/osu,smoogipooo/osu,smoogipoo/osu,DrabWeb/osu,NeoAdonis/osu,EVAST9919/osu,ppy/osu,smoogipoo/osu,DrabWeb/osu,osu-RP/osu-RP,nyaamara/osu,2yangk23/osu,Damnae/osu,2yangk23/osu