hydra-evaluator: handle the case where there is no previous jobset eval

Dependencies

• [2] DDMYFZ5X Fix the jobset unchanged check
• [3] 5SHCWE7X * Prevent repeated evaluation of a jobset with the same inputs. This
• [4] PIMGMGAF Rename hydra_eval_jobs to hydra-eval-jobs
• [5] RXVJFQ5A Evaluator cleanups
• [6] FDE3BJAP * Refactoring.
• [*] N22GPKYT * Put info about logs / build products in the DB.

Change contents

• replacement in src/script/hydra-evaluator at line 113
  [3.2334]→[2.328:393](∅→∅)
  − if (getPrevJobsetEval($db, $jobset, 0)->hash eq $argsHash) {
  [3.2334]

  [3.1961]
  + my $prevEval = getPrevJobsetEval($db, $jobset, 0);

  + if (defined $prevEval && $prevEval->hash eq $argsHash) {