Bug #43659 MTR2 should report worker data for tests when using --parallel > 1

Adding "w# " before the test result
Also enable --parallel=2 so this can be tested.

mysql-test/lib/mtr_report.pm

@@ -71,6 +71,8 @@ sub _mtr_report_test_name ($) {
 
   print _name(), _timestamp();
   printf "%-40s ", $tname;
+  my $worker = $tinfo->{worker};
+  printf "w$worker " if $worker;
 
   return $tname;
 }