Fix parallel dataset reporting and nested fixtures

tests/Fixtures/ParallelNestedDatasets/Datasets/Nested/Users.php

@@ -0,0 +1,6 @@
+<?php
+
+dataset('nested.users', [
+    ['alice'],
+    ['bob'],
+]);

tests/Fixtures/ParallelNestedDatasets/TestFileWithNestedDataset.php

@@ -0,0 +1,5 @@
+<?php
+
+test('loads nested dataset', function (string $name) {
+    expect($name)->not->toBeEmpty();
+})->with('nested.users');