Fix deprecations, replace cookies with localstorage

[millnut]

• Fix a deprecation on spaceless that was missed (see https://www.drupal.org/project/drupal/issues/3094850)
• Remove full-page-alert-banner.es6.js, Drupal doesn't use es6 for builds anymore
• Replace cookie functionality with LocalStorage
  • Cookie storage limit 4KB
  • LocalStorage limit 5MB
• Refactor in plain/vanilla javascript to remove jQuery dependency

[ekes]

https://www.drupal.org/node/3322720

[andybroomfield]

Thanks @millnut.
I'd pause on this for now as js-cookie includes a remote CDN loading dependency unless people know to include it.
Since that would be springing it on people in a patch release, I'd rather wait until that is released before we merge this.

I still think we can rewrite the cookie logic to not require js-cookie if someone has time.

[andybroomfield]

Is this template actully used anywhere? it does not appear in any other custom entitiy. Maybe thats why we havn't noticed it.

[millnut]

Thanks for checking @andybroomfield I wasn't aware it used a remote CDN. If I have the time I'll rewrite in plain javascript and we can probably remove this requirement altogether