extract LibraryPrefixContributor from imported reference contributor

pkg/analysis_server/test/services/completion/dart/test_all.dart

Index: pkg/analysis_server/test/services/completion/dart/test_all.dart
diff --git a/pkg/analysis_server/test/services/completion/dart/test_all.dart b/pkg/analysis_server/test/services/completion/dart/test_all.dart
index 321630da363f72c85fa42642cf7044a839648b4c..a9dc2751d929f7bd875f8a0a09b35fd7dd18ef03 100644
--- a/pkg/analysis_server/test/services/completion/dart/test_all.dart
+++ b/pkg/analysis_server/test/services/completion/dart/test_all.dart
@@ -13,7 +13,8 @@ import 'common_usage_sorter_test.dart' as common_usage_test;
 import 'field_formal_contributor_test.dart' as field_formal_contributor_test;
 import 'inherited_contributor_test.dart' as inherited_contributor_test;
 import 'keyword_contributor_test.dart' as keyword_test;
-import 'library_member_contributor_test.dart' as library_test;
+import 'library_member_contributor_test.dart' as library_member_test;
+import 'library_prefix_contributor_test.dart' as library_prefix_test;
 import 'named_constructor_contributor_test.dart' as named_contributor_test;
 import 'static_member_contributor_test.dart' as static_contributor_test;
 import 'type_member_contributor_test.dart' as type_member_contributor_test;
@@ -29,7 +30,8 @@ main() {
     field_formal_contributor_test.main();
     inherited_contributor_test.main();
     keyword_test.main();
-    library_test.main();
+    library_member_test.main();
+    library_prefix_test.main();
     named_contributor_test.main();
     static_contributor_test.main();
     type_member_contributor_test.main();