Draft: Add dkfiles needed for R(D*)_τe analysis

New dec files are added for signal and background modes needed for the R(D*)_τe analysis, all with uniform generator level cuts - informed by the cuts in the HLT2 builder

cc. @dovombru @chinghua

Status of the testing offline:

• Bd_Dst+DX,eX=cocktail,TightCut,RDstTaueCuts.dec
• Bd_Dst+DsX,taunuenu=cocktail,TightCut,RDstTaueCuts.dec
• Bd_Dst+enu,D0pi+=HQET2,TightCut,RDstTaueCuts.dec
• Bd_Dst+taunu,D0pi+,enunu=HQET2,TightCut,RDstTaueCuts.dec
• Bd_DststXenu,Dst+=cocktail,TightCut,RDstTaueCuts.dec
• Bd_Dststenu,Dst+=CocktailHigher,TightCut,RDstTaueCuts.dec
• Bd_Dststtaunu,D0=cocktail,enunu=TightCuts,RDstTaueCuts.dec
• Bs_Dsststenu,Dst+=cocktail,TightCut,RDstTaueCuts.dec
• Bu_Dst+DX,eX=cocktail,TightCut,RDstTaueCuts.dec
• Bu_Dst+DsX,taunuenu=cocktail,TightCut,RDstTaueCuts.dec
• Bu_DststXenu,Dst+=cocktail,TightCut,RDstTaueCuts.dec
• Bu_Dststenu,Dst+=CocktailHigher,TightCut,tighter,RDstTaueCuts.dec
• Bu_Dststtaunu,D0=cocktail,enunu=TightCuts,RDstTaueCuts.dec
• Bd_Dst+enu,D0pi+=BCL,TightCut,RDstTaueCuts.dec
• Bd_Dst+taunu,D0pi+,enunu=BCL,TightCut,RDstTaueCuts.dec