Use API methods to create filter/editor in CKEditor5Test when not explicitly testing the UI

We can probably improve things a lot more if we add an API-only version of CKEditor5TestBase::addNewFormat() - this is very repetitive in a lot of tests and doesn't add any coverage by itself.

Test failures just with the one commit on the MR. Probably better to do the initial filter creation via the API.

After this, it's still the slowest functional js test, but by about 5 seconds https://git.drupalcode.org/project/drupal/-/jobs/2445430

Seems straight forward and no coverage lost.

Committed and pushed ec27dec315 to 11.x and e28a98acc4 to 11.0.x and 438751f8c2 to 10.4.x and 9c5eccee3f to 10.3.x. Thanks!

nod_ → closed merge request !9199

Extra use of the changed method on 10.4 and 10.3

Committed and pushed 9cefe0e8ee to 10.4.x and 5df500a7a8 to 10.3.x. Thanks!

nod_ → closed merge request !9213

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