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/compiler-cli/test/reflector_host_spec.ts

@@ -38,6 +38,7 @@ describe('reflector_host', () => {
           genDir: '/tmp/project/src/gen/',
           basePath: '/tmp/project/src',
           skipMetadataEmit: false,
+          strictMetadataEmit: false,
           skipTemplateCodegen: false,
           trace: false
         },
@@ -47,6 +48,7 @@ describe('reflector_host', () => {
           genDir: '/tmp/project/gen',
           basePath: '/tmp/project/src/',
           skipMetadataEmit: false,
+          strictMetadataEmit: false,
           skipTemplateCodegen: false,
           trace: false
         },