[ClangImporter] Clean up adjustTypeForConcreteImport, part 1
[ClangImporter] Clean up adjustTypeForConcreteImport, part 1

Use a switch over the import hint to cover most of the special cases.
No functionality change.

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