Fix scoreboard update after rejudging.

Previous buggy flow was something like:
- fetch all submissions that for this team/contest/problem combination
- that are valid
- and have a valid judging

The idea of https://github.com/DOMjudge/domjudge/blob/95df1de7bce91f43600cfcb8760ea85762936614/webapp/src/Service/ScoreboardService.php#L240
was that this would filter the OneToMany collection down to only valid
judgings. This is also what happens on the database side.

However, on the doctrine side, the entity manager keeps a cache, and if
the submission is already in the cache with the full collection of valid
and invalid judgings, it will only merged with new data from the
database query, no data (i.e. no judgings) will magically disappear.

In order to fix this, we explicitly filter on the PHP side. An
alternative would be to add a new `OneToMany` mapping with a `where` on
it and use that.

Fixes #2883

Author: meisterT

webapp/src/Entity/Submission.php

@@ -359,6 +359,16 @@ public function getJudgings(): Collection
         return $this->judgings;
     }
 
+    public function getValidJudging(): ?Judging
+    {
+        foreach ($this->judgings as $j) {
+            if ($j->getValid()) {
+                return $j;
+            }
+        }
+        return null;
+    }
+
     public function setLanguage(?Language $language = null): Submission
     {
         $this->language = $language;
@@ -537,6 +547,16 @@ public function getExternalJudgements(): Collection
         return $this->external_judgements;
     }
 
+    public function getValidExternalJudgement(): ?ExternalJudgement
+    {
+        foreach ($this->external_judgements as $ej) {
+            if ($ej->getValid()) {
+                return $ej;
+            }
+        }
+        return null;
+    }
+
     public function setFileForApi(?FileWithName $fileForApi = null): Submission
     {
         $this->fileForApi = $fileForApi;

webapp/src/Service/ScoreboardService.php

@@ -262,9 +262,9 @@ public function calculateScoreRow(
         foreach ($submissions as $submission) {
             /** @var Judging|ExternalJudgement|null $judging */
             if ($useExternalJudgements) {
-                $judging = $submission->getExternalJudgements()->first() ?: null;
+                $judging = $submission->getValidExternalJudgement();
             } else {
-                $judging = $submission->getJudgings()->first() ?: null;
+                $judging = $submission->getValidJudging();
             }
 
             // three things will happen in the loop in this order: