feat(platform-webworker): deprecate platform-webworker (#30642)

DEPRECATION:

platform-webworker has been around since the initial release of Angular
version 2. It began as an experiment to leverage Angular's rendering
architecture and try something different: to run an entire web application
in a web worker.

We've learned a lot from this experiment, and have come to the conclusion
that pushing entire applications to run in a web worker is not a recipe for
success for most applications. This is due to a number of unresolved issues,
including:

* Poor or non-existent support for web worker APIs in web crawlers/indexers.
* Poor support in build and bundling tooling.

As a result, as of Angular version 8, we are deprecating the
`platform-webworker` APIs in Angular. This consists of both NPM packages,
`@angular/platform-webworker` and `@angular/platform-webworker-dynamic`.

Going forward, we will focus our efforts related to web workers around their
primary use case of offloading CPU-intensive but not critical work.

FW-1339 #resolve

PR Close #30642

packages/platform-webworker-dynamic/src/platform-webworker-dynamic.ts

@@ -16,6 +16,7 @@ export {VERSION} from './version';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const platformWorkerAppDynamic =
     createPlatformFactory(platformCoreDynamic, 'workerAppDynamic', [

packages/platform-webworker-dynamic/src/version.ts

@@ -16,5 +16,6 @@ import {Version} from '@angular/core';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const VERSION = new Version('0.0.0-PLACEHOLDER');