[Distributed] IRGen: Let debug info know about distributed accessor
[Distributed] IRGen: Let debug info know about distributed accessor

Use `emitArtificialFunction` to let debug info know that compiler
is about to generate code for distributed accessor.

glessard/swift,atrick/swift,ahoppen/swift,apple/swift,JGiola/swift,JGiola/swift,glessard/swift,gregomni/swift,rudkx/swift,gregomni/swift,gregomni/swift,atrick/swift,apple/swift,benlangmuir/swift,gregomni/swift,gregomni/swift,atrick/swift,atrick/swift,roambotics/swift,benlangmuir/swift,rudkx/swift,apple/swift,glessard/swift,glessard/swift,atrick/swift,benlangmuir/swift,JGiola/swift,atrick/swift,roambotics/swift,glessard/swift,benlangmuir/swift,roambotics/swift,benlangmuir/swift,ahoppen/swift,apple/swift,roambotics/swift,ahoppen/swift,ahoppen/swift,JGiola/swift,roambotics/swift,apple/swift,apple/swift,rudkx/swift,ahoppen/swift,rudkx/swift,gregomni/swift,JGiola/swift,ahoppen/swift,roambotics/swift,glessard/swift,JGiola/swift,benlangmuir/swift,rudkx/swift,rudkx/swift