feat(compiler): Added "strictMetadataEmit" option to ngc (#10951)

ngc can now validate metadata before emitting to verify it doesn't
contain an error symbol that will result in a runtime error if
it is used by the StaticReflector.

To enable this add the section,

  "angularCompilerOptions": {
    "strictMetadataEmit": true
  }

to the top level of the tsconfig.json file passed to ngc.

Enabled metadata validation for packages that are intended to be
used statically.

modules/@angular/platform-browser/index.ts

@@ -27,5 +27,5 @@ export {WORKER_UI_LOCATION_PROVIDERS} from './src/web_workers/ui/location_provid
 
 export {NgProbeToken} from './src/dom/debug/ng_probe';
 export * from './src/worker_render';
-export * from './src/worker_app';
+export {platformWorkerApp, WorkerAppModule} from './src/worker_app';
 export * from './private_export';