[Sema/Index] Resolve #keyPath components so they can be indexed

Unlike \keypath expressions, only the property components of #keypath
expressions were being resolved, so index wouldn't pick up references for their
qualifying types.

Also fixes a code completion bug where it was reporting members from the Swift
rather than ObjC side of bridged types.

Resolves rdar://problem/61573935

lib/Sema/ConstraintSystem.cpp

@@ -493,6 +493,7 @@ ConstraintLocator *ConstraintSystem::getCalleeLocator(
     case ComponentKind::OptionalChain:
     case ComponentKind::OptionalWrap:
     case ComponentKind::Identity:
+    case ComponentKind::DictionaryKey:
       // These components don't have any callee associated, so just continue.
       break;
     }