IRGen: Split up WitnessTableBuilder into {Fragile,Resilient}WitnessTableBuilder
IRGen: Split up WitnessTableBuilder into {Fragile,Resilient}WitnessTableBuilder

This eliminates the need to 'abandon' the initializer for the
fragile witness table, which resilient conformances do not need
or use.

atrick/swift,tkremenek/swift,xwu/swift,apple/swift,apple/swift,stephentyrone/swift,jmgc/swift,JGiola/swift,stephentyrone/swift,hooman/swift,aschwaighofer/swift,hooman/swift,airspeedswift/swift,atrick/swift,parkera/swift,rudkx/swift,nathawes/swift,parkera/swift,allevato/swift,rudkx/swift,atrick/swift,tkremenek/swift,glessard/swift,airspeedswift/swift,hooman/swift,CodaFi/swift,gregomni/swift,jckarter/swift,harlanhaskins/swift,gregomni/swift,glessard/swift,gregomni/swift,aschwaighofer/swift,nathawes/swift,JGiola/swift,glessard/swift,tkremenek/swift,JGiola/swift,jmgc/swift,roambotics/swift,jmgc/swift,nathawes/swift,apple/swift,stephentyrone/swift,parkera/swift,apple/swift,CodaFi/swift,xwu/swift,ahoppen/swift,atrick/swift,allevato/swift,xwu/swift,parkera/swift,benlangmuir/swift,ahoppen/swift,allevato/swift,parkera/swift,roambotics/swift,hooman/swift,glessard/swift,nathawes/swift,aschwaighofer/swift,glessard/swift,roambotics/swift,rudkx/swift,harlanhaskins/swift,rudkx/swift,CodaFi/swift,ahoppen/swift,benlangmuir/swift,airspeedswift/swift,jckarter/swift,CodaFi/swift,jmgc/swift,allevato/swift,benlangmuir/swift,roambotics/swift,gregomni/swift,stephentyrone/swift,gregomni/swift,parkera/swift,CodaFi/swift,benlangmuir/swift,CodaFi/swift,harlanhaskins/swift,hooman/swift,benlangmuir/swift,xwu/swift,parkera/swift,xwu/swift,harlanhaskins/swift,hooman/swift,parkera/swift,JGiola/swift,airspeedswift/swift,xwu/swift,roambotics/swift,rudkx/swift,ahoppen/swift,glessard/swift,tkremenek/swift,stephentyrone/swift,aschwaighofer/swift,nathawes/swift,jckarter/swift,jckarter/swift,jmgc/swift,rudkx/swift,benlangmuir/swift,allevato/swift,stephentyrone/swift,airspeedswift/swift,jckarter/swift,ahoppen/swift,jckarter/swift,jckarter/swift,nathawes/swift,hooman/swift,harlanhaskins/swift,aschwaighofer/swift,apple/swift,tkremenek/swift,apple/swift,aschwaighofer/swift,nathawes/swift,tkremenek/swift,tkremenek/swift,airspeedswift/swift,xwu/swift,gregomni/swift,roambotics/swift,stephentyrone/swift,allevato/swift,allevato/swift,jmgc/swift,atrick/swift,jmgc/swift,harlanhaskins/swift,atrick/swift,JGiola/swift,JGiola/swift,aschwaighofer/swift,CodaFi/swift,airspeedswift/swift,ahoppen/swift,harlanhaskins/swift