IDE: Clean up traversal logic in SourceEntityWalker
IDE: Clean up traversal logic in SourceEntityWalker

Try to make this a bit more self-documenting.

roambotics/swift,parkera/swift,harlanhaskins/swift,ahoppen/swift,aschwaighofer/swift,jmgc/swift,gregomni/swift,harlanhaskins/swift,jckarter/swift,hooman/swift,nathawes/swift,stephentyrone/swift,airspeedswift/swift,nathawes/swift,harlanhaskins/swift,rudkx/swift,glessard/swift,jmgc/swift,jmgc/swift,gregomni/swift,hooman/swift,allevato/swift,CodaFi/swift,ahoppen/swift,rudkx/swift,allevato/swift,glessard/swift,harlanhaskins/swift,gregomni/swift,jmgc/swift,JGiola/swift,aschwaighofer/swift,benlangmuir/swift,hooman/swift,allevato/swift,aschwaighofer/swift,tkremenek/swift,tkremenek/swift,JGiola/swift,allevato/swift,benlangmuir/swift,aschwaighofer/swift,harlanhaskins/swift,benlangmuir/swift,atrick/swift,xwu/swift,apple/swift,rudkx/swift,atrick/swift,CodaFi/swift,benlangmuir/swift,atrick/swift,tkremenek/swift,parkera/swift,CodaFi/swift,harlanhaskins/swift,benlangmuir/swift,jckarter/swift,rudkx/swift,airspeedswift/swift,harlanhaskins/swift,hooman/swift,nathawes/swift,JGiola/swift,jckarter/swift,atrick/swift,jckarter/swift,jckarter/swift,stephentyrone/swift,jmgc/swift,gregomni/swift,jmgc/swift,ahoppen/swift,JGiola/swift,hooman/swift,rudkx/swift,glessard/swift,parkera/swift,roambotics/swift,tkremenek/swift,xwu/swift,apple/swift,stephentyrone/swift,nathawes/swift,JGiola/swift,apple/swift,allevato/swift,roambotics/swift,airspeedswift/swift,glessard/swift,glessard/swift,xwu/swift,parkera/swift,apple/swift,roambotics/swift,xwu/swift,CodaFi/swift,xwu/swift,gregomni/swift,nathawes/swift,atrick/swift,aschwaighofer/swift,airspeedswift/swift,allevato/swift,aschwaighofer/swift,benlangmuir/swift,parkera/swift,ahoppen/swift,stephentyrone/swift,tkremenek/swift,CodaFi/swift,hooman/swift,allevato/swift,apple/swift,parkera/swift,roambotics/swift,JGiola/swift,gregomni/swift,CodaFi/swift,atrick/swift,stephentyrone/swift,stephentyrone/swift,CodaFi/swift,tkremenek/swift,hooman/swift,jckarter/swift,ahoppen/swift,parkera/swift,roambotics/swift,glessard/swift,airspeedswift/swift,airspeedswift/swift,nathawes/swift,xwu/swift,parkera/swift,rudkx/swift,stephentyrone/swift,jckarter/swift,tkremenek/swift,ahoppen/swift,aschwaighofer/swift,nathawes/swift,apple/swift,xwu/swift,airspeedswift/swift,jmgc/swift