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/playground/src/web_workers/kitchen_sink/index_common.ts

@@ -19,7 +19,7 @@ export class GreetingService {
 // Directives are light-weight. They don't allow new
 // expression contexts (use @Component for those needs).
 @Directive({selector: '[red]'})
-class RedDec {
+export class RedDec {
   // ElementRef is always injectable and it wraps the element on which the
   // directive was found by the compiler.
   constructor(el: ElementRef, renderer: Renderer) {