Generate _runtime.js from dart (dart-archive/dev_compiler#310)

The following part files were ported from the original .js (lib/runtime/dart/_foo.js -> input_sdk/private/foo.dart):
- input_sdk/private/rtti.dart
- input_sdk/private/types.dart
- input_sdk/private/classes.dart
- input_sdk/private/errors.dart
- input_sdk/private/generators.dart
- input_sdk/private/operations.dart
- input_sdk/private/runtime.dart

Notes:
- Introduced genericTypeConstructor intrinsic: `JS('', '#(type)', genericTypeConstructor(List))` generates `core.List$(type)`
- Used new JS quasiquotes everywhere
- Depends on new internal `@JSExportName` annotation to alias symbols like dart.{as, is, const, assert, export, implements, throw, async, dynamic, void} (see https://codereview.chromium.org/1580413002/)

BUG=
[email protected]

Review URL: https://codereview.chromium.org/1530563003 .

Author: Olivier Chafik

pkg/dev_compiler/karma.conf.js

@@ -18,7 +18,6 @@ module.exports = function(config) {
     // list of files / patterns to load in the browser
     files: [
       'lib/runtime/dart_*.js',
-      'lib/runtime/_*.js',
       'lib/runtime/dart/*.js',
       // {pattern: 'test/browser/*.js', included: false}
       'test/codegen/expect/async_helper/async_helper.js',