ExplicitModuleLoader: use a temporary source manager for loading the explicit module map, NFC
ExplicitModuleLoader: use a temporary source manager for loading the explicit module map, NFC

We don't need the buffer for the explicit module map to be persistent in the ASTContext.

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