Swift SIL: add a utility protocol `BridgedRandomAccessCollection`
Swift SIL: add a utility protocol `BridgedRandomAccessCollection`

It fixes the default reflection for bridged random access collections, which usually have a `bridged` stored property.
Conforming to this protocol displays the "real" children of a bridged random access collection and not just `bridged`.

glessard/swift,roambotics/swift,glessard/swift,apple/swift,benlangmuir/swift,benlangmuir/swift,apple/swift,glessard/swift,benlangmuir/swift,roambotics/swift,roambotics/swift,roambotics/swift,glessard/swift,benlangmuir/swift,roambotics/swift,apple/swift,roambotics/swift,glessard/swift,apple/swift,benlangmuir/swift,apple/swift,benlangmuir/swift,glessard/swift,apple/swift