Update branches for new master-next scheme.
Update branches for new master-next scheme.

Combine the "next" and "next-upstream" checkout schemes since the new
approach for maintaining master-next is to building against the
"upstream-with-swift" Clang/LLVM branches. We do not plan to use the
"stable-next" branches anymore. (We can delete those branches after
this transition has had time to settle out.) I have also merged the
"upstream" scheme with "next-upstream" because building the combination
of branches previously in the scheme is not something we expect to work
now.

tjw/swift,codestergit/swift,aschwaighofer/swift,arvedviehweger/swift,sschiau/swift,shajrawi/swift,codestergit/swift,xedin/swift,alblue/swift,austinzheng/swift,tardieu/swift,codestergit/swift,calebd/swift,shahmishal/swift,Jnosh/swift,manavgabhawala/swift,djwbrown/swift,benlangmuir/swift,benlangmuir/swift,milseman/swift,shajrawi/swift,manavgabhawala/swift,brentdax/swift,apple/swift,manavgabhawala/swift,shajrawi/swift,jopamer/swift,gregomni/swift,lorentey/swift,gregomni/swift,parkera/swift,codestergit/swift,deyton/swift,gregomni/swift,alblue/swift,rudkx/swift,tardieu/swift,natecook1000/swift,tjw/swift,hooman/swift,JGiola/swift,devincoughlin/swift,stephentyrone/swift,frootloops/swift,hooman/swift,calebd/swift,xedin/swift,tardieu/swift,djwbrown/swift,felix91gr/swift,nathawes/swift,stephentyrone/swift,natecook1000/swift,alblue/swift,zisko/swift,felix91gr/swift,jckarter/swift,CodaFi/swift,rudkx/swift,jmgc/swift,airspeedswift/swift,JGiola/swift,xedin/swift,nathawes/swift,uasys/swift,hughbe/swift,allevato/swift,zisko/swift,codestergit/swift,gribozavr/swift,jopamer/swift,karwa/swift,devincoughlin/swift,hughbe/swift,swiftix/swift,codestergit/swift,calebd/swift,practicalswift/swift,xedin/swift,arvedviehweger/swift,gribozavr/swift,brentdax/swift,aschwaighofer/swift,xwu/swift,harlanhaskins/swift,roambotics/swift,devincoughlin/swift,djwbrown/swift,glessard/swift,calebd/swift,tardieu/swift,milseman/swift,jtbandes/swift,ahoppen/swift,Jnosh/swift,hughbe/swift,OscarSwanros/swift,apple/swift,amraboelela/swift,jopamer/swift,ahoppen/swift,ahoppen/swift,allevato/swift,nathawes/swift,sschiau/swift,CodaFi/swift,austinzheng/swift,arvedviehweger/swift,milseman/swift,amraboelela/swift,bitjammer/swift,huonw/swift,deyton/swift,bitjammer/swift,tjw/swift,felix91gr/swift,codestergit/swift,brentdax/swift,jopamer/swift,tkremenek/swift,allevato/swift,stephentyrone/swift,felix91gr/swift,karwa/swift,felix91gr/swift,tkremenek/swift,parkera/swift,JGiola/swift,zisko/swift,uasys/swift,ahoppen/swift,roambotics/swift,xwu/swift,deyton/swift,zisko/swift,milseman/swift,alblue/swift,amraboelela/swift,jckarter/swift,gribozavr/swift,tinysun212/swift-windows,karwa/swift,hooman/swift,lorentey/swift,benlangmuir/swift,danielmartin/swift,harlanhaskins/swift,frootloops/swift,tkremenek/swift,tjw/swift,austinzheng/swift,apple/swift,CodaFi/swift,lorentey/swift,milseman/swift,sschiau/swift,shajrawi/swift,austinzheng/swift,hooman/swift,alblue/swift,tardieu/swift,glessard/swift,austinzheng/swift,xwu/swift,stephentyrone/swift,uasys/swift,lorentey/swift,xwu/swift,OscarSwanros/swift,frootloops/swift,shahmishal/swift,huonw/swift,tkremenek/swift,calebd/swift,brentdax/swift,sschiau/swift,tjw/swift,return/swift,uasys/swift,jmgc/swift,jtbandes/swift,xedin/swift,jtbandes/swift,stephentyrone/swift,amraboelela/swift,CodaFi/swift,airspeedswift/swift,amraboelela/swift,uasys/swift,hughbe/swift,tinysun212/swift-windows,tinysun212/swift-windows,nathawes/swift,atrick/swift,deyton/swift,jopamer/swift,tkremenek/swift,huonw/swift,jckarter/swift,swiftix/swift,jtbandes/swift,return/swift,stephentyrone/swift,return/swift,allevato/swift,swiftix/swift,felix91gr/swift,gribozavr/swift,shajrawi/swift,karwa/swift,arvedviehweger/swift,xwu/swift,tinysun212/swift-windows,OscarSwanros/swift,devincoughlin/swift,karwa/swift,shahmishal/swift,airspeedswift/swift,hughbe/swift,ahoppen/swift,return/swift,atrick/swift,jckarter/swift,harlanhaskins/swift,devincoughlin/swift,milseman/swift,aschwaighofer/swift,calebd/swift,gribozavr/swift,uasys/swift,amraboelela/swift,airspeedswift/swift,atrick/swift,brentdax/swift,rudkx/swift,shajrawi/swift,manavgabhawala/swift,huonw/swift,return/swift,shahmishal/swift,zisko/swift,djwbrown/swift,parkera/swift,natecook1000/swift,apple/swift,sschiau/swift,huonw/swift,devincoughlin/swift,sschiau/swift,jopamer/swift,hughbe/swift,sschiau/swift,rudkx/swift,roambotics/swift,xedin/swift,jckarter/swift,aschwaighofer/swift,bitjammer/swift,milseman/swift,danielmartin/swift,allevato/swift,xedin/swift,harlanhaskins/swift,OscarSwanros/swift,brentdax/swift,jopamer/swift,shahmishal/swift,ahoppen/swift,atrick/swift,arvedviehweger/swift,xwu/swift,gregomni/swift,devincoughlin/swift,natecook1000/swift,practicalswift/swift,return/swift,benlangmuir/swift,bitjammer/swift,devincoughlin/swift,shajrawi/swift,deyton/swift,airspeedswift/swift,tjw/swift,gregomni/swift,karwa/swift,CodaFi/swift,karwa/swift,tinysun212/swift-windows,jckarter/swift,deyton/swift,harlanhaskins/swift,gribozavr/swift,harlanhaskins/swift,aschwaighofer/swift,apple/swift,hooman/swift,manavgabhawala/swift,CodaFi/swift,airspeedswift/swift,aschwaighofer/swift,huonw/swift,Jnosh/swift,danielmartin/swift,zisko/swift,frootloops/swift,jmgc/swift,tinysun212/swift-windows,roambotics/swift,natecook1000/swift,practicalswift/swift,practicalswift/swift,arvedviehweger/swift,hooman/swift,natecook1000/swift,natecook1000/swift,tkremenek/swift,tardieu/swift,roambotics/swift,practicalswift/swift,tinysun212/swift-windows,allevato/swift,jmgc/swift,lorentey/swift,bitjammer/swift,huonw/swift,karwa/swift,OscarSwanros/swift,practicalswift/swift,austinzheng/swift,practicalswift/swift,uasys/swift,lorentey/swift,nathawes/swift,swiftix/swift,lorentey/swift,manavgabhawala/swift,roambotics/swift,hooman/swift,zisko/swift,return/swift,danielmartin/swift,practicalswift/swift,rudkx/swift,shahmishal/swift,glessard/swift,parkera/swift,danielmartin/swift,parkera/swift,tkremenek/swift,JGiola/swift,jckarter/swift,shajrawi/swift,parkera/swift,arvedviehweger/swift,stephentyrone/swift,djwbrown/swift,Jnosh/swift,parkera/swift,bitjammer/swift,jmgc/swift,frootloops/swift,swiftix/swift,djwbrown/swift,apple/swift,amraboelela/swift,glessard/swift,calebd/swift,glessard/swift,alblue/swift,xwu/swift,harlanhaskins/swift,danielmartin/swift,benlangmuir/swift,parkera/swift,aschwaighofer/swift,CodaFi/swift,glessard/swift,manavgabhawala/swift,tardieu/swift,Jnosh/swift,Jnosh/swift,OscarSwanros/swift,sschiau/swift,bitjammer/swift,allevato/swift,felix91gr/swift,benlangmuir/swift,deyton/swift,frootloops/swift,hughbe/swift,alblue/swift,swiftix/swift,JGiola/swift,jtbandes/swift,jtbandes/swift,shahmishal/swift,gribozavr/swift,JGiola/swift,OscarSwanros/swift,atrick/swift,lorentey/swift,nathawes/swift,Jnosh/swift,rudkx/swift,austinzheng/swift,xedin/swift,atrick/swift,airspeedswift/swift,gregomni/swift,frootloops/swift,danielmartin/swift,brentdax/swift,jmgc/swift,gribozavr/swift,tjw/swift,swiftix/swift,jmgc/swift,jtbandes/swift,djwbrown/swift,nathawes/swift,shahmishal/swift