psql: Add tests for repeated calls of \bind[_named]

The implementation assumes that on multiple calls of these meta-commands
the last one wins.  Multiple \g calls in-between mean multiple
executions.

There were no tests to check these properties, hence let's add
something.

Author: Jelte Fennema-Nio, Michael Paquier
Discussion: https://postgr.es/m/CAGECzQSTE7CoM=Gst56Xj8pOvjaPr09+7jjtWqTC40pGETyAuA@mail.gmail.com

src/test/regress/expected/psql.out

@@ -141,6 +141,25 @@ SELECT $1, $2 \parse stmt3
 ERROR:  there is no parameter $1
 LINE 1: SELECT $1, $2 
                ^
+-- Last \bind_named wins
+\bind_named stmt2 'foo' \bind_named stmt3 'foo2' 'bar2' \g
+ ?column? | ?column? 
+----------+----------
+ foo2     | bar2
+(1 row)
+
+-- Multiple \g calls mean multiple executions
+\bind_named stmt2 'foo3' \g \bind_named stmt3 'foo4' 'bar4' \g
+ ?column? 
+----------
+ foo3
+(1 row)
+
+ ?column? | ?column? 
+----------+----------
+ foo4     | bar4
+(1 row)
+
 -- \close (extended query protocol)
 \close
 \close: missing required argument
@@ -173,6 +192,25 @@ SELECT $1, $2 \bind 'foo' 'bar' \g
  foo      | bar
 (1 row)
 
+-- last \bind wins
+select $1::int as col \bind 'foo' \bind 2 \g
+ col 
+-----
+   2
+(1 row)
+
+-- Multiple \g calls mean multiple executions
+select $1::int as col \bind 1 \g \bind 2 \g
+ col 
+-----
+   1
+(1 row)
+
+ col 
+-----
+   2
+(1 row)
+
 -- errors
 -- parse error
 SELECT foo \bind \g

src/test/regress/sql/psql.sql

@@ -63,6 +63,10 @@ SELECT $1, $2 \parse stmt3
 \bind_named stmt4
 \bind_named
 \g
+-- Last \bind_named wins
+\bind_named stmt2 'foo' \bind_named stmt3 'foo2' 'bar2' \g
+-- Multiple \g calls mean multiple executions
+\bind_named stmt2 'foo3' \g \bind_named stmt3 'foo4' 'bar4' \g
 
 -- \close (extended query protocol)
 \close
@@ -76,6 +80,11 @@ SELECT 1 \bind \g
 SELECT $1 \bind 'foo' \g
 SELECT $1, $2 \bind 'foo' 'bar' \g
 
+-- last \bind wins
+select $1::int as col \bind 'foo' \bind 2 \g
+-- Multiple \g calls mean multiple executions
+select $1::int as col \bind 1 \g \bind 2 \g
+
 -- errors
 -- parse error
 SELECT foo \bind \g