Re-apply "staging for move to PlaygroundSupport" (#4215)
Re-apply "staging for move to PlaygroundSupport" (#4215)

Reverts apple/swift#4196; swift-corelibs-foundation is still depending on it.
natecook1000/swift,tjw/swift,nathawes/swift,return/swift,jckarter/swift,JaSpa/swift,xedin/swift,tardieu/swift,jtbandes/swift,parkera/swift,jckarter/swift,gmilos/swift,IngmarStein/swift,xedin/swift,lorentey/swift,kperryua/swift,rudkx/swift,gmilos/swift,lorentey/swift,brentdax/swift,felix91gr/swift,ben-ng/swift,frootloops/swift,danielmartin/swift,milseman/swift,airspeedswift/swift,JGiola/swift,xedin/swift,karwa/swift,jopamer/swift,tjw/swift,JaSpa/swift,codestergit/swift,Jnosh/swift,xwu/swift,OscarSwanros/swift,alblue/swift,austinzheng/swift,practicalswift/swift,harlanhaskins/swift,manavgabhawala/swift,lorentey/swift,ahoppen/swift,xwu/swift,CodaFi/swift,IngmarStein/swift,modocache/swift,manavgabhawala/swift,hughbe/swift,uasys/swift,jmgc/swift,codestergit/swift,roambotics/swift,allevato/swift,milseman/swift,swiftix/swift,harlanhaskins/swift,gottesmm/swift,gmilos/swift,shahmishal/swift,benlangmuir/swift,allevato/swift,return/swift,natecook1000/swift,gottesmm/swift,danielmartin/swift,bitjammer/swift,jckarter/swift,kperryua/swift,apple/swift,zisko/swift,jckarter/swift,deyton/swift,aschwaighofer/swift,tjw/swift,nathawes/swift,djwbrown/swift,apple/swift,therealbnut/swift,CodaFi/swift,kstaring/swift,jckarter/swift,milseman/swift,tjw/swift,gregomni/swift,harlanhaskins/swift,brentdax/swift,natecook1000/swift,Jnosh/swift,deyton/swift,milseman/swift,hooman/swift,Jnosh/swift,gmilos/swift,swiftix/swift,hooman/swift,tjw/swift,harlanhaskins/swift,lorentey/swift,JGiola/swift,airspeedswift/swift,tinysun212/swift-windows,CodaFi/swift,gregomni/swift,kstaring/swift,swiftix/swift,codestergit/swift,jtbandes/swift,devincoughlin/swift,swiftix/swift,tinysun212/swift-windows,jopamer/swift,shahmishal/swift,tardieu/swift,Jnosh/swift,tjw/swift,gribozavr/swift,hooman/swift,jopamer/swift,swiftix/swift,sschiau/swift,arvedviehweger/swift,austinzheng/swift,rudkx/swift,airspeedswift/swift,austinzheng/swift,JaSpa/swift,hughbe/swift,gottesmm/swift,shahmishal/swift,tkremenek/swift,modocache/swift,jtbandes/swift,xedin/swift,sschiau/swift,bitjammer/swift,shajrawi/swift,djwbrown/swift,allevato/swift,manavgabhawala/swift,devincoughlin/swift,natecook1000/swift,therealbnut/swift,arvedviehweger/swift,tardieu/swift,uasys/swift,aschwaighofer/swift,stephentyrone/swift,shajrawi/swift,tkremenek/swift,glessard/swift,manavgabhawala/swift,felix91gr/swift,airspeedswift/swift,nathawes/swift,return/swift,calebd/swift,zisko/swift,manavgabhawala/swift,codestergit/swift,glessard/swift,gregomni/swift,stephentyrone/swift,gottesmm/swift,codestergit/swift,allevato/swift,IngmarStein/swift,huonw/swift,manavgabhawala/swift,felix91gr/swift,apple/swift,gottesmm/swift,ben-ng/swift,Jnosh/swift,alblue/swift,therealbnut/swift,allevato/swift,nathawes/swift,aschwaighofer/swift,uasys/swift,djwbrown/swift,karwa/swift,kstaring/swift,parkera/swift,return/swift,parkera/swift,stephentyrone/swift,sschiau/swift,practicalswift/swift,JaSpa/swift,JGiola/swift,danielmartin/swift,apple/swift,IngmarStein/swift,danielmartin/swift,deyton/swift,ben-ng/swift,milseman/swift,hughbe/swift,glessard/swift,jckarter/swift,aschwaighofer/swift,gmilos/swift,frootloops/swift,tinysun212/swift-windows,return/swift,tinysun212/swift-windows,arvedviehweger/swift,tjw/swift,gribozavr/swift,allevato/swift,tkremenek/swift,deyton/swift,danielmartin/swift,gottesmm/swift,tinysun212/swift-windows,devincoughlin/swift,JaSpa/swift,aschwaighofer/swift,xwu/swift,glessard/swift,JGiola/swift,shahmishal/swift,ben-ng/swift,karwa/swift,tkremenek/swift,felix91gr/swift,jopamer/swift,lorentey/swift,amraboelela/swift,bitjammer/swift,huonw/swift,alblue/swift,Jnosh/swift,zisko/swift,xedin/swift,JGiola/swift,gribozavr/swift,aschwaighofer/swift,OscarSwanros/swift,calebd/swift,gmilos/swift,xwu/swift,atrick/swift,shahmishal/swift,parkera/swift,shajrawi/swift,allevato/swift,jmgc/swift,jopamer/swift,airspeedswift/swift,ahoppen/swift,CodaFi/swift,nathawes/swift,rudkx/swift,bitjammer/swift,tinysun212/swift-windows,codestergit/swift,hooman/swift,ahoppen/swift,kstaring/swift,felix91gr/swift,jmgc/swift,practicalswift/swift,djwbrown/swift,IngmarStein/swift,modocache/swift,felix91gr/swift,manavgabhawala/swift,lorentey/swift,deyton/swift,zisko/swift,therealbnut/swift,austinzheng/swift,hughbe/swift,benlangmuir/swift,djwbrown/swift,gribozavr/swift,ahoppen/swift,karwa/swift,calebd/swift,therealbnut/swift,jckarter/swift,JaSpa/swift,zisko/swift,huonw/swift,bitjammer/swift,practicalswift/swift,devincoughlin/swift,stephentyrone/swift,natecook1000/swift,nathawes/swift,tinysun212/swift-windows,xedin/swift,jtbandes/swift,devincoughlin/swift,gregomni/swift,hooman/swift,stephentyrone/swift,gribozavr/swift,benlangmuir/swift,alblue/swift,jtbandes/swift,zisko/swift,sschiau/swift,djwbrown/swift,ahoppen/swift,kperryua/swift,uasys/swift,kperryua/swift,kperryua/swift,bitjammer/swift,bitjammer/swift,brentdax/swift,shahmishal/swift,milseman/swift,jtbandes/swift,tkremenek/swift,kstaring/swift,shajrawi/swift,frootloops/swift,brentdax/swift,hooman/swift,atrick/swift,hooman/swift,OscarSwanros/swift,kperryua/swift,return/swift,roambotics/swift,arvedviehweger/swift,sschiau/swift,jmgc/swift,ben-ng/swift,harlanhaskins/swift,djwbrown/swift,roambotics/swift,rudkx/swift,hughbe/swift,alblue/swift,uasys/swift,huonw/swift,swiftix/swift,OscarSwanros/swift,alblue/swift,harlanhaskins/swift,ben-ng/swift,shahmishal/swift,gottesmm/swift,lorentey/swift,stephentyrone/swift,xwu/swift,return/swift,brentdax/swift,tkremenek/swift,harlanhaskins/swift,parkera/swift,hughbe/swift,amraboelela/swift,frootloops/swift,therealbnut/swift,airspeedswift/swift,alblue/swift,amraboelela/swift,austinzheng/swift,danielmartin/swift,devincoughlin/swift,natecook1000/swift,xedin/swift,parkera/swift,CodaFi/swift,glessard/swift,jopamer/swift,sschiau/swift,modocache/swift,parkera/swift,roambotics/swift,huonw/swift,shajrawi/swift,amraboelela/swift,practicalswift/swift,felix91gr/swift,shahmishal/swift,arvedviehweger/swift,xedin/swift,kstaring/swift,calebd/swift,frootloops/swift,apple/swift,amraboelela/swift,lorentey/swift,sschiau/swift,brentdax/swift,IngmarStein/swift,rudkx/swift,ahoppen/swift,parkera/swift,karwa/swift,glessard/swift,frootloops/swift,jmgc/swift,karwa/swift,jtbandes/swift,therealbnut/swift,huonw/swift,arvedviehweger/swift,atrick/swift,amraboelela/swift,ben-ng/swift,practicalswift/swift,kperryua/swift,codestergit/swift,zisko/swift,practicalswift/swift,gribozavr/swift,deyton/swift,natecook1000/swift,karwa/swift,arvedviehweger/swift,xwu/swift,IngmarStein/swift,CodaFi/swift,hughbe/swift,tkremenek/swift,atrick/swift,benlangmuir/swift,uasys/swift,devincoughlin/swift,airspeedswift/swift,atrick/swift,atrick/swift,gregomni/swift,shajrawi/swift,CodaFi/swift,tardieu/swift,OscarSwanros/swift,stephentyrone/swift,benlangmuir/swift,uasys/swift,practicalswift/swift,OscarSwanros/swift,roambotics/swift,milseman/swift,kstaring/swift,karwa/swift,danielmartin/swift,tardieu/swift,JGiola/swift,apple/swift,Jnosh/swift,calebd/swift,jmgc/swift,nathawes/swift,modocache/swift,jmgc/swift,amraboelela/swift,deyton/swift,austinzheng/swift,modocache/swift,jopamer/swift,tardieu/swift,aschwaighofer/swift,JaSpa/swift,shajrawi/swift,modocache/swift,OscarSwanros/swift,rudkx/swift,gmilos/swift,gregomni/swift,shajrawi/swift,devincoughlin/swift,roambotics/swift,calebd/swift,tardieu/swift,xwu/swift,gribozavr/swift,brentdax/swift,huonw/swift,swiftix/swift,sschiau/swift,frootloops/swift,calebd/swift,benlangmuir/swift,austinzheng/swift,gribozavr/swift