remove CompletionCache and obsolete tests, and cleanup imports

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

Index: pkg/analysis_server/test/services/completion/test_all.dart
diff --git a/pkg/analysis_server/test/services/completion/test_all.dart b/pkg/analysis_server/test/services/completion/test_all.dart
index a47c7c81b2f1949634a82388032490a8fcb94e45..d6b119e189d621c8309ee6639bb8b67ea20c5bad 100644
--- a/pkg/analysis_server/test/services/completion/test_all.dart
+++ b/pkg/analysis_server/test/services/completion/test_all.dart
@@ -7,8 +7,6 @@ library test.services.completion;
 import 'package:unittest/unittest.dart';
 
 import '../../utils.dart';
-import 'completion_computer_test.dart' as completion_computer_test;
-import 'completion_manager_test.dart' as completion_manager_test;
 import 'completion_target_test.dart' as completion_target_test;
 import 'dart/test_all.dart' as dart_contributor_tests;
 import 'optype_test.dart' as optype_test;
@@ -17,8 +15,6 @@ import 'optype_test.dart' as optype_test;
 main() {
   initializeTestEnvironment();
   group('completion', () {
-    completion_computer_test.main();
-    completion_manager_test.main();
     completion_target_test.main();
     dart_contributor_tests.main();
     optype_test.main();