build: remove references to tsc-wrapped (#19298)

With this commit `ngc` is used instead of `tsc-wrapped` for
collecting metadata and tsickle rewriting and `tsc-wrapped`
is removed from the repository.

`@angular/tsc-wrapped@5` is now deprecated and is no longer
used, updated, or maintained as part as of Angular 5.x.x.

`@angular/tsc-wrapped@4` is still maintained and required by
Angular 4.x.x and will be maintained as long as 4.x.x is in
LTS.

PR Close #19298

packages/compiler/testing/index.ts

@@ -11,4 +11,4 @@
 // replaces this file with production index.ts when it rewrites private symbol
 // names.
 
-export * from './public_api';
+export * from './testing';

packages/compiler/testing/testing.ts

@@ -0,0 +1,14 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+// This file is not used to build this module. It is only used during editing
+// by the TypeScript language service and during build for verification. `ngc`
+// replaces this file with production index.ts when it rewrites private symbol
+// names.
+
+export * from './public_api';

packages/compiler/testing/tsconfig-build.json

@@ -5,19 +5,20 @@
     "baseUrl": ".",
     "rootDir": "../",
     "paths": {
-      "@angular/compiler": ["../../../dist/packages/compiler"]
+      "@angular/compiler": ["../../../dist/packages/compiler"],
+      "@angular/core": ["../../../dist/packages/core"]
     },
     "outDir": "../../../dist/packages/compiler"
   },
 
   "files": [
-    "public_api.ts",
+    "testing.ts",
     "../../../node_modules/zone.js/dist/zone.js.d.ts"
   ],
 
   "angularCompilerOptions": {
     "annotateForClosureCompiler": true,
-    "flatModuleOutFile": "testing.js",
-    "flatModuleId": "@angular/compiler/testing"
+    "skipMetadataEmit": true,
+    "skipTemplateCodegen": true
   }
 }