[CodeCompletion] Only show type annotations for macros that return non-void

Showing the type annotation only makes sense if they are not `Void`. That’s consistent with functions where we also don’t show a `Void` return type. Most importantly, we shouldn’t be showing a `Void` type annotation for attached macros.

rdar://108870970

Author: ahoppen

include/swift/IDE/CompletionLookup.h

@@ -324,6 +324,12 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
 
   bool isUnresolvedMemberIdealType(Type Ty);
 
+  /// Creates a \c CodeCompletionResultBuilder in this lookup’s sink and sets
+  /// the current expected type context in it
+  CodeCompletionResultBuilder
+  makeResultBuilder(CodeCompletionResultKind kind,
+                    SemanticContextKind semanticContext) const;
+
   void addValueBaseName(CodeCompletionResultBuilder &Builder,
                         DeclBaseName Name);