ext/pgsql: adding pg_put_copy_data/pg_put_copy_end.

pg_put_copy_data allows to send COPY commands to the server.
pg_put_copy_end signals the end of the n commands.

Both return 3 states ; 1, 0 and -1 when 1 is success, 0 the buffer queue
is full then -1 for errors.

Close GH-14325

ext/pgsql/pgsql.stub.php

@@ -949,6 +949,9 @@ namespace {
 #endif
 
     function pg_change_password(PgSql\Connection $connection, string $user, #[\SensitiveParameter] string $password): bool {}
+
+    function pg_put_copy_data(PgSql\Connection $connection, string $cmd): int {}
+    function pg_put_copy_end(PgSql\Connection $connection, string $error = null): int {}
 }
 
 namespace PgSql {