[Diagnostics] Let invalid member ref carry member declaration instead of looking it up

All places where `invalid member ref` fix/diagnostic is used already
have a reference to the potential member choice declaration, which
diagnostic could take advantage of.

lib/Sema/CSSimplify.cpp

@@ -4530,8 +4530,12 @@ fixMemberRef(ConstraintSystem &cs, Type baseTy,
   if (reason) {
     switch (*reason) {
     case MemberLookupResult::UR_InstanceMemberOnType:
-    case MemberLookupResult::UR_TypeMemberOnInstance:
-      return AllowTypeOrInstanceMember::create(cs, baseTy, memberName, locator);
+    case MemberLookupResult::UR_TypeMemberOnInstance: {
+      return choice.isDecl()
+                 ? AllowTypeOrInstanceMember::create(
+                       cs, baseTy, choice.getDecl(), memberName, locator)
+                 : nullptr;
+    }
 
     case MemberLookupResult::UR_Inaccessible:
       assert(choice.isDecl());