psql: Rename meta-command \close to \close_prepared

\close has been introduced in d55322b0da to be able to close a
prepared statement using the extended protocol in psql.  Per discussion,
the name "close" is ambiguous.  At the SQL level, CLOSE is used to close
a cursor.  At protocol level, the close message can be used to either
close a statement or a portal.

This patch renames \close to \close_prepared to avoid any ambiguity and
make it clear that this is used to close a prepared statement.  This new
name has been chosen based on the feedback from the author and the
reviewers.

Author: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Jelte Fennema-Nio <postgres@jeltef.nl>
Discussion: https://postgr.es/m/3e694442-0df5-4f92-a08f-c5d4c4346b85@eisentraut.org

src/test/regress/expected/psql.out

@@ -160,12 +160,12 @@ LINE 1: SELECT $1, $2
  foo4     | bar4
 (1 row)
 
--- \close (extended query protocol)
-\close
-\close: missing required argument
-\close ''
-\close stmt2
-\close stmt2
+-- \close_prepared (extended query protocol)
+\close_prepared
+\close_prepared: missing required argument
+\close_prepared ''
+\close_prepared stmt2
+\close_prepared stmt2
 SELECT name, statement FROM pg_prepared_statements ORDER BY name;
  name  |   statement    
 -------+----------------
@@ -4666,7 +4666,7 @@ bar 'bar' "bar"
 	\C arg1
 	\c arg1 arg2 arg3 arg4
 	\cd arg1
-	\close stmt1
+	\close_prepared stmt1
 	\conninfo
 	\copy arg1 arg2 arg3 arg4 arg5 arg6
 	\copyright

src/test/regress/expected/psql_pipeline.out

@@ -564,7 +564,7 @@ SELECT $1 \bind \sendpipeline
 SELECT $1 \bind 1 \sendpipeline
 SELECT $1 \parse a
 \bind_named a 1 \sendpipeline
-\close a
+\close_prepared a
 \flushrequest
 \getresults
 ERROR:  bind message supplies 0 parameters, but prepared statement "" requires 1
@@ -572,7 +572,7 @@ ERROR:  bind message supplies 0 parameters, but prepared statement "" requires 1
 SELECT $1 \bind 1 \sendpipeline
 SELECT $1 \parse a
 \bind_named a 1 \sendpipeline
-\close a
+\close_prepared a
 -- Sync allows pipeline to recover.
 \syncpipeline
 \getresults
@@ -580,7 +580,7 @@ Pipeline aborted, command did not run
 SELECT $1 \bind 1 \sendpipeline
 SELECT $1 \parse a
 \bind_named a 1 \sendpipeline
-\close a
+\close_prepared a
 \flushrequest
 \getresults
  ?column? 

src/test/regress/sql/psql.sql

@@ -68,11 +68,11 @@ SELECT $1, $2 \parse stmt3
 -- Multiple \g calls mean multiple executions
 \bind_named stmt2 'foo3' \g \bind_named stmt3 'foo4' 'bar4' \g
 
--- \close (extended query protocol)
-\close
-\close ''
-\close stmt2
-\close stmt2
+-- \close_prepared (extended query protocol)
+\close_prepared
+\close_prepared ''
+\close_prepared stmt2
+\close_prepared stmt2
 SELECT name, statement FROM pg_prepared_statements ORDER BY name;
 
 -- \bind (extended query protocol)
@@ -1035,7 +1035,7 @@ select \if false \\ (bogus \else \\ 42 \endif \\ forty_two;
 	\C arg1
 	\c arg1 arg2 arg3 arg4
 	\cd arg1
-	\close stmt1
+	\close_prepared stmt1
 	\conninfo
 	\copy arg1 arg2 arg3 arg4 arg5 arg6
 	\copyright

src/test/regress/sql/psql_pipeline.sql

@@ -306,21 +306,21 @@ SELECT $1 \bind \sendpipeline
 SELECT $1 \bind 1 \sendpipeline
 SELECT $1 \parse a
 \bind_named a 1 \sendpipeline
-\close a
+\close_prepared a
 \flushrequest
 \getresults
 -- Pipeline is aborted.
 SELECT $1 \bind 1 \sendpipeline
 SELECT $1 \parse a
 \bind_named a 1 \sendpipeline
-\close a
+\close_prepared a
 -- Sync allows pipeline to recover.
 \syncpipeline
 \getresults
 SELECT $1 \bind 1 \sendpipeline
 SELECT $1 \parse a
 \bind_named a 1 \sendpipeline
-\close a
+\close_prepared a
 \flushrequest
 \getresults
 \endpipeline