[BUGFIX] More deterministic mm sorting

A 'true' MM relation (select / group with MM, but not inline
with foreign_field - used in core for pages/tt_content table
to sys_category via sys_category_record_mm) has two sorting
fields: 'sorting' for the local (sys_category) side, and
'sorting_foreign' for the foreign (pages / tt_content) side.

When categories are added to a tt_content element,
'sorting_foreign' is set to the given order of sys_category
elements. 'sorting' is set to 0. When then opening a
sys_category record that has multiple records pointing to
it with 0 as sorting, the returned order of records is
non-deterministic and depends on implicit DB engine fallbacks.

This also confuses the reference index, which checks
refindex integrity always from the 'local' side.

The patch adds 'uid_foreign' as second order-by field to
force deterministic ordering. There is still a possible
collision in multi table relations (more than one foreign
table uses the mm table like pages AND tt_content to
sys_category with foreign records having the same uid) and
if the mm table allows "multi" relations. Those scenarios
however have no explicit TCA configuration (only implicit
via MM_match_fields), need a deeper investigation and
possibly further detail patches later.

The patch should for now fix a functional test that is
flaky with postgres.

Change-Id: I3c89d0e67f8a4065354f9df173020ca0080e0d57
Resolves: #93075
Releases: master, 10.4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67110
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>

typo3/sysext/core/Classes/Database/ReferenceIndex.php

@@ -927,6 +927,7 @@ public function updateIndex($testOnly, ?ProgressListenerInterface $progressListe
                 $queryResult = $queryBuilder
                     ->select(...$fields)
                     ->from($tableName)
+                    ->orderBy('uid')
                     ->execute();
             } catch (DBALException $e) {
                 // Table exists in TCA but does not exist in the database

typo3/sysext/core/Classes/Database/RelationHandler.php

@@ -593,6 +593,7 @@ public function readMM($tableName, $uid)
             )
         );
         $queryBuilder->orderBy($sorting_field);
+        $queryBuilder->addOrderBy($uidForeign_field);
         $statement = $queryBuilder->execute();
         while ($row = $statement->fetch()) {
             // Default