[sil-cast-optimizer] Fix a bridging related bug
[sil-cast-optimizer] Fix a bridging related bug

- Try harder when looking for an implementation of _bridgeToObjectiveC. Consider extensions, super types, protocols, etc.
- If it cannot be found, simply bail instead of asserting.

No test-case is provided, because it is a bit difficult to create a self-contained test. The issue only happens when there are overlays and multiple modules in play. I'll try to come up with a test-case later.

This fixes radar://problem/30261147

glessard/swift,airspeedswift/swift,arvedviehweger/swift,atrick/swift,jopamer/swift,codestergit/swift,JGiola/swift,danielmartin/swift,swiftix/swift,hooman/swift,devincoughlin/swift,atrick/swift,uasys/swift,CodaFi/swift,karwa/swift,uasys/swift,deyton/swift,zisko/swift,gribozavr/swift,alblue/swift,shahmishal/swift,atrick/swift,harlanhaskins/swift,deyton/swift,tkremenek/swift,huonw/swift,austinzheng/swift,sschiau/swift,swiftix/swift,milseman/swift,swiftix/swift,uasys/swift,xwu/swift,felix91gr/swift,zisko/swift,glessard/swift,xedin/swift,OscarSwanros/swift,arvedviehweger/swift,benlangmuir/swift,devincoughlin/swift,swiftix/swift,OscarSwanros/swift,gribozavr/swift,tjw/swift,Jnosh/swift,bitjammer/swift,tardieu/swift,harlanhaskins/swift,bitjammer/swift,lorentey/swift,airspeedswift/swift,jtbandes/swift,JGiola/swift,jmgc/swift,aschwaighofer/swift,airspeedswift/swift,tinysun212/swift-windows,CodaFi/swift,felix91gr/swift,jopamer/swift,tjw/swift,lorentey/swift,austinzheng/swift,huonw/swift,brentdax/swift,gregomni/swift,shajrawi/swift,natecook1000/swift,tinysun212/swift-windows,shahmishal/swift,amraboelela/swift,shahmishal/swift,jmgc/swift,devincoughlin/swift,nathawes/swift,brentdax/swift,JGiola/swift,arvedviehweger/swift,karwa/swift,djwbrown/swift,arvedviehweger/swift,zisko/swift,huonw/swift,deyton/swift,gregomni/swift,hooman/swift,benlangmuir/swift,rudkx/swift,danielmartin/swift,xedin/swift,tinysun212/swift-windows,allevato/swift,brentdax/swift,amraboelela/swift,tjw/swift,parkera/swift,arvedviehweger/swift,alblue/swift,codestergit/swift,brentdax/swift,aschwaighofer/swift,djwbrown/swift,shahmishal/swift,devincoughlin/swift,ahoppen/swift,frootloops/swift,felix91gr/swift,JGiola/swift,return/swift,milseman/swift,gribozavr/swift,jtbandes/swift,devincoughlin/swift,alblue/swift,frootloops/swift,austinzheng/swift,amraboelela/swift,Jnosh/swift,danielmartin/swift,sschiau/swift,frootloops/swift,jckarter/swift,allevato/swift,shahmishal/swift,gribozavr/swift,xedin/swift,practicalswift/swift,tardieu/swift,amraboelela/swift,sschiau/swift,harlanhaskins/swift,tkremenek/swift,deyton/swift,frootloops/swift,stephentyrone/swift,xwu/swift,rudkx/swift,roambotics/swift,aschwaighofer/swift,danielmartin/swift,alblue/swift,zisko/swift,nathawes/swift,stephentyrone/swift,gregomni/swift,tjw/swift,natecook1000/swift,return/swift,hughbe/swift,JGiola/swift,jtbandes/swift,milseman/swift,codestergit/swift,jckarter/swift,jckarter/swift,sschiau/swift,aschwaighofer/swift,tkremenek/swift,practicalswift/swift,sschiau/swift,jtbandes/swift,austinzheng/swift,lorentey/swift,codestergit/swift,lorentey/swift,frootloops/swift,nathawes/swift,manavgabhawala/swift,austinzheng/swift,xedin/swift,uasys/swift,JGiola/swift,brentdax/swift,calebd/swift,frootloops/swift,sschiau/swift,ahoppen/swift,roambotics/swift,Jnosh/swift,jopamer/swift,lorentey/swift,alblue/swift,tardieu/swift,tjw/swift,jckarter/swift,Jnosh/swift,glessard/swift,jckarter/swift,sschiau/swift,jmgc/swift,karwa/swift,Jnosh/swift,tjw/swift,allevato/swift,natecook1000/swift,huonw/swift,parkera/swift,hooman/swift,karwa/swift,gregomni/swift,uasys/swift,deyton/swift,practicalswift/swift,allevato/swift,allevato/swift,karwa/swift,djwbrown/swift,milseman/swift,nathawes/swift,xwu/swift,apple/swift,lorentey/swift,roambotics/swift,tinysun212/swift-windows,parkera/swift,djwbrown/swift,CodaFi/swift,manavgabhawala/swift,shahmishal/swift,tardieu/swift,xedin/swift,manavgabhawala/swift,rudkx/swift,austinzheng/swift,OscarSwanros/swift,karwa/swift,hughbe/swift,bitjammer/swift,calebd/swift,tkremenek/swift,apple/swift,milseman/swift,amraboelela/swift,benlangmuir/swift,glessard/swift,deyton/swift,manavgabhawala/swift,uasys/swift,milseman/swift,tkremenek/swift,parkera/swift,zisko/swift,jckarter/swift,OscarSwanros/swift,glessard/swift,arvedviehweger/swift,bitjammer/swift,xwu/swift,hooman/swift,brentdax/swift,atrick/swift,felix91gr/swift,nathawes/swift,shajrawi/swift,hughbe/swift,ahoppen/swift,huonw/swift,natecook1000/swift,danielmartin/swift,brentdax/swift,manavgabhawala/swift,Jnosh/swift,apple/swift,apple/swift,harlanhaskins/swift,OscarSwanros/swift,nathawes/swift,devincoughlin/swift,gregomni/swift,shajrawi/swift,hooman/swift,shajrawi/swift,jtbandes/swift,aschwaighofer/swift,tjw/swift,ahoppen/swift,natecook1000/swift,amraboelela/swift,jmgc/swift,aschwaighofer/swift,alblue/swift,practicalswift/swift,huonw/swift,calebd/swift,shajrawi/swift,return/swift,OscarSwanros/swift,calebd/swift,parkera/swift,calebd/swift,jopamer/swift,manavgabhawala/swift,tkremenek/swift,karwa/swift,stephentyrone/swift,CodaFi/swift,manavgabhawala/swift,danielmartin/swift,roambotics/swift,hughbe/swift,swiftix/swift,OscarSwanros/swift,apple/swift,felix91gr/swift,zisko/swift,practicalswift/swift,calebd/swift,xedin/swift,roambotics/swift,lorentey/swift,tinysun212/swift-windows,ahoppen/swift,jtbandes/swift,harlanhaskins/swift,deyton/swift,jopamer/swift,tardieu/swift,hooman/swift,stephentyrone/swift,codestergit/swift,shahmishal/swift,harlanhaskins/swift,xwu/swift,CodaFi/swift,zisko/swift,stephentyrone/swift,allevato/swift,djwbrown/swift,ahoppen/swift,airspeedswift/swift,practicalswift/swift,tinysun212/swift-windows,gregomni/swift,shajrawi/swift,aschwaighofer/swift,danielmartin/swift,parkera/swift,rudkx/swift,rudkx/swift,xedin/swift,bitjammer/swift,return/swift,roambotics/swift,hughbe/swift,felix91gr/swift,lorentey/swift,codestergit/swift,CodaFi/swift,shajrawi/swift,shahmishal/swift,bitjammer/swift,tardieu/swift,return/swift,parkera/swift,felix91gr/swift,shajrawi/swift,karwa/swift,arvedviehweger/swift,Jnosh/swift,frootloops/swift,devincoughlin/swift,tardieu/swift,jopamer/swift,practicalswift/swift,gribozavr/swift,harlanhaskins/swift,alblue/swift,parkera/swift,calebd/swift,glessard/swift,huonw/swift,allevato/swift,swiftix/swift,amraboelela/swift,hooman/swift,gribozavr/swift,jtbandes/swift,benlangmuir/swift,benlangmuir/swift,jmgc/swift,hughbe/swift,gribozavr/swift,return/swift,atrick/swift,return/swift,sschiau/swift,gribozavr/swift,codestergit/swift,stephentyrone/swift,jmgc/swift,jckarter/swift,milseman/swift,airspeedswift/swift,apple/swift,atrick/swift,natecook1000/swift,uasys/swift,xedin/swift,hughbe/swift,jmgc/swift,devincoughlin/swift,djwbrown/swift,jopamer/swift,tkremenek/swift,djwbrown/swift,bitjammer/swift,xwu/swift,airspeedswift/swift,CodaFi/swift,stephentyrone/swift,nathawes/swift,benlangmuir/swift,rudkx/swift,tinysun212/swift-windows,austinzheng/swift,swiftix/swift,natecook1000/swift,xwu/swift,airspeedswift/swift,practicalswift/swift