[Runtime] Give some structure to witness tables.
[Runtime] Give some structure to witness tables.

Make it easier to access the protocol conformance descriptor.

rudkx/swift,apple/swift,gregomni/swift,huonw/swift,nathawes/swift,devincoughlin/swift,JGiola/swift,xedin/swift,jopamer/swift,sschiau/swift,tkremenek/swift,natecook1000/swift,jmgc/swift,stephentyrone/swift,gribozavr/swift,airspeedswift/swift,devincoughlin/swift,shahmishal/swift,practicalswift/swift,devincoughlin/swift,jopamer/swift,xwu/swift,lorentey/swift,brentdax/swift,JGiola/swift,austinzheng/swift,zisko/swift,gribozavr/swift,jopamer/swift,gribozavr/swift,lorentey/swift,nathawes/swift,tkremenek/swift,jckarter/swift,tkremenek/swift,CodaFi/swift,shajrawi/swift,hooman/swift,devincoughlin/swift,parkera/swift,hooman/swift,airspeedswift/swift,sschiau/swift,xwu/swift,allevato/swift,xedin/swift,gregomni/swift,benlangmuir/swift,danielmartin/swift,lorentey/swift,stephentyrone/swift,karwa/swift,glessard/swift,CodaFi/swift,allevato/swift,jmgc/swift,amraboelela/swift,shajrawi/swift,rudkx/swift,glessard/swift,atrick/swift,aschwaighofer/swift,ahoppen/swift,ahoppen/swift,CodaFi/swift,practicalswift/swift,harlanhaskins/swift,practicalswift/swift,benlangmuir/swift,hooman/swift,parkera/swift,zisko/swift,stephentyrone/swift,danielmartin/swift,karwa/swift,parkera/swift,rudkx/swift,shajrawi/swift,tjw/swift,alblue/swift,karwa/swift,apple/swift,atrick/swift,stephentyrone/swift,lorentey/swift,tjw/swift,devincoughlin/swift,ahoppen/swift,CodaFi/swift,allevato/swift,brentdax/swift,harlanhaskins/swift,xedin/swift,CodaFi/swift,atrick/swift,zisko/swift,tkremenek/swift,brentdax/swift,sschiau/swift,roambotics/swift,shahmishal/swift,austinzheng/swift,xedin/swift,rudkx/swift,allevato/swift,aschwaighofer/swift,austinzheng/swift,harlanhaskins/swift,sschiau/swift,allevato/swift,natecook1000/swift,gregomni/swift,jmgc/swift,lorentey/swift,parkera/swift,danielmartin/swift,shajrawi/swift,parkera/swift,tkremenek/swift,sschiau/swift,austinzheng/swift,apple/swift,nathawes/swift,alblue/swift,natecook1000/swift,brentdax/swift,jckarter/swift,practicalswift/swift,alblue/swift,jmgc/swift,glessard/swift,natecook1000/swift,karwa/swift,tjw/swift,glessard/swift,shajrawi/swift,huonw/swift,practicalswift/swift,amraboelela/swift,danielmartin/swift,harlanhaskins/swift,jmgc/swift,amraboelela/swift,nathawes/swift,shahmishal/swift,xwu/swift,alblue/swift,austinzheng/swift,zisko/swift,amraboelela/swift,xwu/swift,xwu/swift,stephentyrone/swift,gribozavr/swift,jmgc/swift,lorentey/swift,jopamer/swift,allevato/swift,jopamer/swift,benlangmuir/swift,natecook1000/swift,huonw/swift,tkremenek/swift,aschwaighofer/swift,sschiau/swift,atrick/swift,gregomni/swift,nathawes/swift,gribozavr/swift,harlanhaskins/swift,hooman/swift,brentdax/swift,aschwaighofer/swift,shajrawi/swift,devincoughlin/swift,huonw/swift,sschiau/swift,shahmishal/swift,lorentey/swift,zisko/swift,benlangmuir/swift,jckarter/swift,benlangmuir/swift,practicalswift/swift,natecook1000/swift,xedin/swift,shajrawi/swift,apple/swift,jckarter/swift,shahmishal/swift,hooman/swift,shahmishal/swift,karwa/swift,brentdax/swift,jckarter/swift,hooman/swift,gribozavr/swift,tkremenek/swift,shahmishal/swift,roambotics/swift,parkera/swift,JGiola/swift,alblue/swift,austinzheng/swift,roambotics/swift,shajrawi/swift,karwa/swift,airspeedswift/swift,zisko/swift,JGiola/swift,brentdax/swift,airspeedswift/swift,aschwaighofer/swift,tjw/swift,apple/swift,amraboelela/swift,airspeedswift/swift,karwa/swift,tjw/swift,zisko/swift,practicalswift/swift,rudkx/swift,atrick/swift,jopamer/swift,gregomni/swift,JGiola/swift,devincoughlin/swift,apple/swift,huonw/swift,rudkx/swift,karwa/swift,natecook1000/swift,roambotics/swift,xedin/swift,tjw/swift,devincoughlin/swift,xedin/swift,stephentyrone/swift,amraboelela/swift,jopamer/swift,aschwaighofer/swift,amraboelela/swift,danielmartin/swift,ahoppen/swift,glessard/swift,tjw/swift,xwu/swift,airspeedswift/swift,airspeedswift/swift,roambotics/swift,roambotics/swift,huonw/swift,alblue/swift,harlanhaskins/swift,glessard/swift,nathawes/swift,ahoppen/swift,shahmishal/swift,parkera/swift,sschiau/swift,austinzheng/swift,allevato/swift,gribozavr/swift,CodaFi/swift,practicalswift/swift,xedin/swift,JGiola/swift,parkera/swift,jmgc/swift,jckarter/swift,nathawes/swift,gribozavr/swift,hooman/swift,gregomni/swift,atrick/swift,CodaFi/swift,aschwaighofer/swift,stephentyrone/swift,benlangmuir/swift,harlanhaskins/swift,huonw/swift,xwu/swift,jckarter/swift,danielmartin/swift,danielmartin/swift,ahoppen/swift,lorentey/swift,alblue/swift