Extract 'DartUnitHighlightsComputer' tests into a separate file.

pkg/analysis_server/test/test_all.dart

Index: pkg/analysis_server/test/test_all.dart
diff --git a/pkg/analysis_server/test/test_all.dart b/pkg/analysis_server/test/test_all.dart
index 33499679ecb8735ac70a15b52a87c2f495e2aa96..831436faf8ad3892ff015be4d32beac62d886c15 100644
--- a/pkg/analysis_server/test/test_all.dart
+++ b/pkg/analysis_server/test/test_all.dart
@@ -4,6 +4,7 @@
 
 import 'package:unittest/unittest.dart';
 
+import 'analysis_notification_highlights_test.dart' as analysis_notification_highlights_test;
 import 'analysis_notification_navigation_test.dart' as analysis_notification_navigation_test;
 import 'analysis_notification_outline_test.dart' as analysis_notification_outline_test;
 import 'analysis_server_test.dart' as analysis_server_test;
@@ -27,6 +28,7 @@ import 'socket_server_test.dart' as socket_server_test;
 main() {
   groupSep = ' | ';
   group('analysis_server', () {
+    analysis_notification_highlights_test.main();
     analysis_notification_navigation_test.main();
     analysis_notification_outline_test.main();
     analysis_server_test.main();