ClangImporter: Clean up inheritance clause synthesis
ClangImporter: Clean up inheritance clause synthesis

There was some duplicate code for adding protocols to inheritance
clauses and constructing the SynthesizedProtocolAttrs that indicate
a conformance should have a LazyConformanceLoader.

Clean this up to make it less error-prone.

NFC for now, until further changes land.

zisko/swift,xwu/swift,xedin/swift,gribozavr/swift,gregomni/swift,natecook1000/swift,allevato/swift,shahmishal/swift,natecook1000/swift,CodaFi/swift,benlangmuir/swift,xedin/swift,shahmishal/swift,tkremenek/swift,jmgc/swift,sschiau/swift,lorentey/swift,jopamer/swift,benlangmuir/swift,airspeedswift/swift,shajrawi/swift,CodaFi/swift,aschwaighofer/swift,zisko/swift,huonw/swift,amraboelela/swift,amraboelela/swift,JGiola/swift,sschiau/swift,karwa/swift,jmgc/swift,brentdax/swift,atrick/swift,ahoppen/swift,xwu/swift,lorentey/swift,lorentey/swift,stephentyrone/swift,nathawes/swift,tkremenek/swift,roambotics/swift,harlanhaskins/swift,frootloops/swift,benlangmuir/swift,shajrawi/swift,alblue/swift,airspeedswift/swift,gregomni/swift,karwa/swift,shajrawi/swift,aschwaighofer/swift,devincoughlin/swift,alblue/swift,airspeedswift/swift,austinzheng/swift,gribozavr/swift,allevato/swift,shajrawi/swift,amraboelela/swift,hooman/swift,apple/swift,ahoppen/swift,glessard/swift,brentdax/swift,xwu/swift,parkera/swift,huonw/swift,gribozavr/swift,aschwaighofer/swift,atrick/swift,frootloops/swift,karwa/swift,airspeedswift/swift,parkera/swift,zisko/swift,tjw/swift,roambotics/swift,parkera/swift,karwa/swift,tkremenek/swift,uasys/swift,allevato/swift,jopamer/swift,swiftix/swift,xwu/swift,roambotics/swift,gribozavr/swift,shajrawi/swift,glessard/swift,austinzheng/swift,JGiola/swift,jckarter/swift,sschiau/swift,hooman/swift,jmgc/swift,frootloops/swift,brentdax/swift,xedin/swift,tkremenek/swift,tkremenek/swift,xwu/swift,harlanhaskins/swift,aschwaighofer/swift,frootloops/swift,ahoppen/swift,xedin/swift,JGiola/swift,uasys/swift,benlangmuir/swift,jopamer/swift,jmgc/swift,natecook1000/swift,gregomni/swift,danielmartin/swift,amraboelela/swift,sschiau/swift,alblue/swift,uasys/swift,swiftix/swift,shahmishal/swift,airspeedswift/swift,tjw/swift,frootloops/swift,shajrawi/swift,austinzheng/swift,OscarSwanros/swift,huonw/swift,xedin/swift,shahmishal/swift,huonw/swift,OscarSwanros/swift,jckarter/swift,nathawes/swift,zisko/swift,shajrawi/swift,jopamer/swift,hooman/swift,rudkx/swift,harlanhaskins/swift,ahoppen/swift,CodaFi/swift,uasys/swift,roambotics/swift,jmgc/swift,natecook1000/swift,allevato/swift,alblue/swift,harlanhaskins/swift,tjw/swift,shahmishal/swift,devincoughlin/swift,danielmartin/swift,practicalswift/swift,roambotics/swift,CodaFi/swift,OscarSwanros/swift,jopamer/swift,uasys/swift,xedin/swift,parkera/swift,parkera/swift,OscarSwanros/swift,danielmartin/swift,tjw/swift,xedin/swift,lorentey/swift,jckarter/swift,jmgc/swift,swiftix/swift,swiftix/swift,amraboelela/swift,zisko/swift,parkera/swift,alblue/swift,natecook1000/swift,danielmartin/swift,atrick/swift,jckarter/swift,zisko/swift,swiftix/swift,atrick/swift,harlanhaskins/swift,stephentyrone/swift,allevato/swift,gregomni/swift,airspeedswift/swift,tjw/swift,lorentey/swift,stephentyrone/swift,practicalswift/swift,gribozavr/swift,brentdax/swift,zisko/swift,xedin/swift,practicalswift/swift,jckarter/swift,austinzheng/swift,karwa/swift,lorentey/swift,atrick/swift,jmgc/swift,hooman/swift,sschiau/swift,sschiau/swift,natecook1000/swift,apple/swift,xwu/swift,brentdax/swift,devincoughlin/swift,hooman/swift,OscarSwanros/swift,lorentey/swift,practicalswift/swift,brentdax/swift,stephentyrone/swift,jopamer/swift,brentdax/swift,CodaFi/swift,gribozavr/swift,roambotics/swift,karwa/swift,danielmartin/swift,harlanhaskins/swift,nathawes/swift,apple/swift,practicalswift/swift,devincoughlin/swift,sschiau/swift,tkremenek/swift,hooman/swift,rudkx/swift,gregomni/swift,swiftix/swift,CodaFi/swift,shahmishal/swift,gribozavr/swift,apple/swift,nathawes/swift,aschwaighofer/swift,rudkx/swift,devincoughlin/swift,ahoppen/swift,austinzheng/swift,rudkx/swift,ahoppen/swift,apple/swift,huonw/swift,devincoughlin/swift,huonw/swift,uasys/swift,CodaFi/swift,uasys/swift,devincoughlin/swift,swiftix/swift,nathawes/swift,amraboelela/swift,danielmartin/swift,stephentyrone/swift,lorentey/swift,natecook1000/swift,practicalswift/swift,frootloops/swift,danielmartin/swift,austinzheng/swift,harlanhaskins/swift,JGiola/swift,karwa/swift,rudkx/swift,practicalswift/swift,tjw/swift,alblue/swift,glessard/swift,jopamer/swift,JGiola/swift,benlangmuir/swift,jckarter/swift,hooman/swift,parkera/swift,huonw/swift,sschiau/swift,austinzheng/swift,aschwaighofer/swift,shahmishal/swift,apple/swift,alblue/swift,nathawes/swift,allevato/swift,JGiola/swift,rudkx/swift,glessard/swift,tkremenek/swift,airspeedswift/swift,glessard/swift,stephentyrone/swift,frootloops/swift,aschwaighofer/swift,OscarSwanros/swift,devincoughlin/swift,gregomni/swift,xwu/swift,parkera/swift,jckarter/swift,gribozavr/swift,karwa/swift,OscarSwanros/swift,tjw/swift,atrick/swift,glessard/swift,stephentyrone/swift,shahmishal/swift,practicalswift/swift,allevato/swift,shajrawi/swift,nathawes/swift,benlangmuir/swift,amraboelela/swift