Filter settings override in url_embed.schema.yml breaks filter settings

Thanks for the catch! This makes sense and comports with the syntax used in Drupal core & elsewhere for filter format settings.

Tests are failing as expected: "current major" has an issue with Twitter output, and "next major" does not have a compatible version of drupal/embed to use. Proceeding to merge, as 3.x is in alpha currently, anyway.

Automatically closed - issue fixed for 2 weeks with no activity.