Print DEBUG2 like that rather than as DEBUG

DEBUG is an alias for DEBUG2, but we want DEBUG2 to show in the settings
no matter how it was spelled.

Takeshi Ideriha

Discussion: https://postgr.es/m/4E72940DA2BF16479384A86D54D0988A5678EC03@G01JPEXMBKW04

src/backend/utils/misc/guc.c

@@ -216,12 +216,12 @@ static const struct config_enum_entry bytea_output_options[] = {
  * they sort slightly different (see "log" level)
  */
 static const struct config_enum_entry client_message_level_options[] = {
-	{"debug", DEBUG2, true},
 	{"debug5", DEBUG5, false},
 	{"debug4", DEBUG4, false},
 	{"debug3", DEBUG3, false},
 	{"debug2", DEBUG2, false},
 	{"debug1", DEBUG1, false},
+	{"debug", DEBUG2, true},
 	{"log", LOG, false},
 	{"info", INFO, true},
 	{"notice", NOTICE, false},
@@ -233,12 +233,12 @@ static const struct config_enum_entry client_message_level_options[] = {
 };
 
 static const struct config_enum_entry server_message_level_options[] = {
-	{"debug", DEBUG2, true},
 	{"debug5", DEBUG5, false},
 	{"debug4", DEBUG4, false},
 	{"debug3", DEBUG3, false},
 	{"debug2", DEBUG2, false},
 	{"debug1", DEBUG1, false},
+	{"debug", DEBUG2, true},
 	{"info", INFO, false},
 	{"notice", NOTICE, false},
 	{"warning", WARNING, false},