fix(docs-infra): support recovering from unrecoverable SW states (#39651)

Occasionally, the SW would end up in a broken state where some of the
eagerly cached resources of an older version were available in the local
cache, but others (such as lazy-loaded bundles) were not. This would
leave the app in a broken state and a blank screen would be displayed.
See #28114 for a more detailed discussion.

This commit takes advantage of the newly introduced (in v11)
[SwUpdate#unrecoverable][1] API to detect these bad states and recover
by doing a full page reload whenever an [UnrecoverableStateEvent][2] is
emitted.

Partially addresses #28114.

NOTE:
Currently, `SwUpdate.unrecoverable` only works if the app has already
bootstrapped; i.e. if only lazy-loaded bundles have been purged from the
cache.
That should be fine in practice, since the cache entries are removed in
least-recently-used order. Thus the eagerly loaded bundles will be the
last to be removed from the cache (which rarely happens in practice).

[1]: https://v11.angular.io/api/service-worker/SwUpdate#unrecoverable
[2]: https://v11.angular.io/api/service-worker/UnrecoverableStateEvent

PR Close #39651

aio/src/testing/location.service.ts

@@ -13,6 +13,7 @@ export class MockLocationService {
               .callFake((url: string) => this.urlSubject.next(url));
   goExternal = jasmine.createSpy('Location.goExternal');
   replace = jasmine.createSpy('Location.replace');
+  reloadPage = jasmine.createSpy('Location.reloadPage');
   handleAnchorClick = jasmine.createSpy('Location.handleAnchorClick')
       .and.returnValue(false); // prevent click from causing a browser navigation