[CodeComplete] Offer code completion for attached macro attributes

We need to teach code completion how to invoke the type checker for attached macro attributes. After that, everything started working.

rdar://105232015

lib/AST/Decl.cpp

@@ -445,8 +445,7 @@ void Decl::forEachAttachedMacro(MacroRole role,
 MacroDecl *Decl::getResolvedMacro(CustomAttr *customAttr) const {
   auto declRef = evaluateOrDefault(
       getASTContext().evaluator,
-      ResolveMacroRequest{customAttr, this},
-      ConcreteDeclRef());
+      ResolveMacroRequest{customAttr, getDeclContext()}, ConcreteDeclRef());
 
   return dyn_cast_or_null<MacroDecl>(declRef.getDecl());
 }