[semantic-arc-opts] Perform a rename/add some comments after talking with @atrick.
[semantic-arc-opts] Perform a rename/add some comments after talking with @atrick.

This should add additional clarity to the pass's impl.

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