Issue #3469900: Added hook_module_implements_alter to force migrate_plus hook to execute first.

Closes #3469900

migrate_plus.module

@@ -92,3 +92,16 @@ function migrate_plus_migration_plugins_alter(array &$migrations): void {
 function migrate_plus_migrate_prepare_row(Row $row, MigrateSourceInterface $source, MigrationInterface $migration): void {
   \Drupal::service('event_dispatcher')->dispatch(new MigratePrepareRowEvent($row, $source, $migration), MigrateEvents::PREPARE_ROW);
 }
+
+/**
+ * Implements hook_module_implements_alter().
+ */
+function migrate_plus_module_implements_alter(&$implementations, $hook) {
+  switch ($hook) {
+    // Merge shared_configuration early so it is available in other migration_plugins_alter.
+    case 'migration_plugins_alter':
+      unset($implementations['migrate_plus']);
+      $implementations = array_merge(['migrate_plus' => false], $implementations);
+      break;
+  }
+}