Fix regression tests for <=14

Author: kovmir

expected/formats_2.out

@@ -0,0 +1,57 @@
+-- explain output on PG12/13 is missing "Async Capable"
+select setting::int < 140000 as pg12_13 from pg_settings where name = 'server_version_num';
+ pg12_13 
+---------
+ f
+(1 row)
+
+-- json output
+set pg_show_plans.plan_format = 'json';
+ERROR:  parameter "pg_show_plans.plan_format" cannot be changed without restarting the server
+show pg_show_plans.plan_format;
+ pg_show_plans.plan_format 
+---------------------------
+ text
+(1 row)
+
+select * from nest();
+ level | plan 
+-------+------
+(0 rows)
+
+-- yaml output
+set pg_show_plans.plan_format = 'yaml';
+ERROR:  parameter "pg_show_plans.plan_format" cannot be changed without restarting the server
+show pg_show_plans.plan_format;
+ pg_show_plans.plan_format 
+---------------------------
+ text
+(1 row)
+
+select * from nest();
+ level | plan 
+-------+------
+(0 rows)
+
+-- xml output
+set pg_show_plans.plan_format = 'xml';
+ERROR:  parameter "pg_show_plans.plan_format" cannot be changed without restarting the server
+show pg_show_plans.plan_format;
+ pg_show_plans.plan_format 
+---------------------------
+ text
+(1 row)
+
+select * from nest();
+ level | plan 
+-------+------
+(0 rows)
+
+-- check plan format after reconnect
+\c
+show pg_show_plans.plan_format;
+ pg_show_plans.plan_format 
+---------------------------
+ text
+(1 row)
+

expected/pg_show_plans_1.out

@@ -0,0 +1,42 @@
+create extension pg_show_plans;
+show pg_show_plans.is_enabled;
+ pg_show_plans.is_enabled 
+--------------------------
+ off
+(1 row)
+
+show pg_show_plans.max_plan_length;
+ pg_show_plans.max_plan_length 
+-------------------------------
+ 16384
+(1 row)
+
+create function nest()
+  returns table (level int, plan text)
+  language plpgsql
+as $$
+  begin
+    return query
+      select pg_show_plans.level, pg_show_plans.plan from pg_show_plans
+        where pg_show_plans.level >= 0;
+  end;
+$$;
+-- text output
+set pg_show_plans.plan_format = 'text';
+ERROR:  parameter "pg_show_plans.plan_format" cannot be changed without restarting the server
+show pg_show_plans.plan_format;
+ pg_show_plans.plan_format 
+---------------------------
+ text
+(1 row)
+
+select level, plan from pg_show_plans;
+ level | plan 
+-------+------
+(0 rows)
+
+select * from nest();
+ level | plan 
+-------+------
+(0 rows)
+