[Serialization] Unify ExistentialMetatype and Metatype deserialization
[Serialization] Unify ExistentialMetatype and Metatype deserialization

harlanhaskins/swift,CodaFi/swift,jckarter/swift,CodaFi/swift,ahoppen/swift,stephentyrone/swift,devincoughlin/swift,hooman/swift,gribozavr/swift,glessard/swift,allevato/swift,karwa/swift,CodaFi/swift,ahoppen/swift,tkremenek/swift,nathawes/swift,glessard/swift,CodaFi/swift,harlanhaskins/swift,parkera/swift,shajrawi/swift,ahoppen/swift,hooman/swift,karwa/swift,shajrawi/swift,devincoughlin/swift,karwa/swift,xwu/swift,allevato/swift,airspeedswift/swift,sschiau/swift,parkera/swift,lorentey/swift,tkremenek/swift,airspeedswift/swift,allevato/swift,atrick/swift,roambotics/swift,glessard/swift,jmgc/swift,apple/swift,benlangmuir/swift,jmgc/swift,xwu/swift,rudkx/swift,hooman/swift,nathawes/swift,rudkx/swift,JGiola/swift,gribozavr/swift,hooman/swift,xwu/swift,aschwaighofer/swift,shahmishal/swift,sschiau/swift,parkera/swift,allevato/swift,lorentey/swift,jckarter/swift,apple/swift,jckarter/swift,tkremenek/swift,devincoughlin/swift,shahmishal/swift,benlangmuir/swift,jckarter/swift,karwa/swift,JGiola/swift,rudkx/swift,roambotics/swift,atrick/swift,benlangmuir/swift,airspeedswift/swift,benlangmuir/swift,jmgc/swift,gribozavr/swift,tkremenek/swift,roambotics/swift,tkremenek/swift,devincoughlin/swift,stephentyrone/swift,xedin/swift,xedin/swift,stephentyrone/swift,shahmishal/swift,jckarter/swift,airspeedswift/swift,karwa/swift,roambotics/swift,nathawes/swift,atrick/swift,shahmishal/swift,devincoughlin/swift,shahmishal/swift,xedin/swift,hooman/swift,aschwaighofer/swift,benlangmuir/swift,shajrawi/swift,glessard/swift,devincoughlin/swift,aschwaighofer/swift,shahmishal/swift,aschwaighofer/swift,atrick/swift,gregomni/swift,gregomni/swift,gribozavr/swift,JGiola/swift,benlangmuir/swift,aschwaighofer/swift,jmgc/swift,karwa/swift,jckarter/swift,lorentey/swift,stephentyrone/swift,sschiau/swift,gregomni/swift,harlanhaskins/swift,allevato/swift,nathawes/swift,JGiola/swift,jckarter/swift,gribozavr/swift,gribozavr/swift,ahoppen/swift,nathawes/swift,apple/swift,apple/swift,parkera/swift,roambotics/swift,xedin/swift,lorentey/swift,sschiau/swift,xwu/swift,sschiau/swift,lorentey/swift,airspeedswift/swift,glessard/swift,apple/swift,allevato/swift,CodaFi/swift,JGiola/swift,apple/swift,shajrawi/swift,glessard/swift,stephentyrone/swift,aschwaighofer/swift,airspeedswift/swift,shajrawi/swift,JGiola/swift,harlanhaskins/swift,shajrawi/swift,roambotics/swift,atrick/swift,xedin/swift,allevato/swift,lorentey/swift,devincoughlin/swift,shajrawi/swift,hooman/swift,xedin/swift,nathawes/swift,devincoughlin/swift,stephentyrone/swift,shajrawi/swift,gribozavr/swift,gregomni/swift,xwu/swift,jmgc/swift,harlanhaskins/swift,parkera/swift,atrick/swift,CodaFi/swift,parkera/swift,harlanhaskins/swift,harlanhaskins/swift,gregomni/swift,hooman/swift,nathawes/swift,rudkx/swift,sschiau/swift,jmgc/swift,tkremenek/swift,CodaFi/swift,xedin/swift,jmgc/swift,gregomni/swift,stephentyrone/swift,airspeedswift/swift,xwu/swift,aschwaighofer/swift,sschiau/swift,ahoppen/swift,karwa/swift,shahmishal/swift,tkremenek/swift,gribozavr/swift,ahoppen/swift,lorentey/swift,xedin/swift,rudkx/swift,xwu/swift,lorentey/swift,shahmishal/swift,sschiau/swift,parkera/swift,rudkx/swift,parkera/swift,karwa/swift