Apply more consistent style for command options in TAP tests

This commit reshapes the grammar of some commands to apply a more
consistent style across the board, following rules similar to
ce1b0f9da0:
- Elimination of some pointless used-once variables.
- Use of long options, to self-document better the options used.
- Use of fat commas to link option names and their assigned values,
including redirections, so as perltidy can be tricked to put them
together.

Author: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Discussion: https://postgr.es/m/87jz8rzf3h.fsf@wibble.ilmari.org

contrib/basebackup_to_shell/t/001_basic.pl

@@ -131,8 +131,10 @@ sub verify_backup
 
 		# Untar.
 		my $extract_path = PostgreSQL::Test::Utils::tempdir;
-		system_or_bail($tar, 'xf', $backup_dir . '/' . $prefix . 'base.tar',
-			'-C', $extract_path);
+		system_or_bail(
+			$tar,
+			'xf' => $backup_dir . '/' . $prefix . 'base.tar',
+			'-C' => $extract_path);
 
 		# Verify.
 		$node->command_ok(