[stdlib] Refactor generic floating-point conversion fast paths
[stdlib] Refactor generic floating-point conversion fast paths

atrick/swift,JGiola/swift,roambotics/swift,jmgc/swift,apple/swift,roambotics/swift,tkremenek/swift,ahoppen/swift,JGiola/swift,gregomni/swift,glessard/swift,glessard/swift,tkremenek/swift,tkremenek/swift,hooman/swift,benlangmuir/swift,apple/swift,xwu/swift,tkremenek/swift,apple/swift,nathawes/swift,jmgc/swift,roambotics/swift,parkera/swift,rudkx/swift,glessard/swift,gregomni/swift,jmgc/swift,tkremenek/swift,gregomni/swift,atrick/swift,xwu/swift,parkera/swift,glessard/swift,tkremenek/swift,parkera/swift,rudkx/swift,apple/swift,jmgc/swift,tkremenek/swift,hooman/swift,nathawes/swift,ahoppen/swift,parkera/swift,hooman/swift,benlangmuir/swift,ahoppen/swift,nathawes/swift,hooman/swift,roambotics/swift,benlangmuir/swift,rudkx/swift,gregomni/swift,parkera/swift,apple/swift,nathawes/swift,JGiola/swift,nathawes/swift,ahoppen/swift,nathawes/swift,parkera/swift,ahoppen/swift,roambotics/swift,glessard/swift,rudkx/swift,jmgc/swift,JGiola/swift,hooman/swift,jmgc/swift,atrick/swift,atrick/swift,xwu/swift,JGiola/swift,hooman/swift,gregomni/swift,benlangmuir/swift,parkera/swift,jmgc/swift,JGiola/swift,benlangmuir/swift,atrick/swift,xwu/swift,nathawes/swift,parkera/swift,xwu/swift,atrick/swift,benlangmuir/swift,glessard/swift,gregomni/swift,xwu/swift,ahoppen/swift,xwu/swift,roambotics/swift,rudkx/swift,hooman/swift,apple/swift,rudkx/swift