patch 9.1.0629: Rename of pum hl_group is incomplete

Problem:  Rename of pum hl_group is incomplete in source.
Solution: Also rename the test function.  Rename to user_hlattr in code
          to avoid confusion with pum_extra.  Add test with matched text
          highlighting (zeertzjq).

closes: #15348

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index a33d6be..c1ed03b 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -359,7 +359,7 @@
 	compl_match_array[i].pum_info = NULL;
 	compl_match_array[i].pum_extra = NULL;
 	compl_match_array[i].pum_kind = NULL;
-	compl_match_array[i].pum_extrahlattr = -1;
+	compl_match_array[i].pum_user_hlattr = -1;
     }
 
     // Compute the popup menu starting column