Decouple service worker from manifest through a dedicated "service worker submodule"

Alright, this should be all done now. After running "drush updb" I still get an apparent manifest.json schema error, but after clearing all cashes it's not there anymore.

Should we find the right caches to clear on update hook? Or let the user run it himself?
Furthermore, we still need to clear the old service worker inside our update hook.

But this can be reviewed already. 🙂

Ok, I understood the service worker cache version now, pretty smart!

// When Drupal replaces `cacheVersion` during server-side processing, it includes
// the packaged version number. That means any module upgrade will automatically
// result in a fresh SW installation.

So basically the cache version of the service worker is generated by the integer set in the configuration + the "version" from the info.yml. Meaning the old service worker will discard itself on update!! :)

We should also manually reset the cache version config to 1 on every update! So the admins can up them manually and don't have to start from their old cache version!

Now we only need to clear the correct caches for the manifest.

Alright, all done. As internally discussed with @Anybody, we'll simply flush all caches on update, since it would take too long, to pin point the correct caches to clear here. Final review pls! :)