Support eslint 9

I've been updating our non-Drupal projects to the new config file format. It's a bit different, but Drupal's configs are not enormous so it should not be very difficut. I don't think backward compatibility will be a problem because eslint 8 supports the config format.

The new config format is kind of confusing but it looks like it might be useful.

Playing around with the compat layer and eslint-config-drupal I found a couple things to keep an eye one that are kinda blocking.

1. airbnb config isn't ready. Think this is the right issue tracking it. https://github.com/airbnb/javascript/issues/2804
2. plugin-import isn't ready https://github.com/import-js/eslint-plugin-import/issues/2948
3. valid-jsdoc was removed which will require some changes. https://github.com/eslint/eslint/issues/15820

Seems like things are still catching up in the community so don't know if the other plugins need changes to support v9 but that could be a problem.

Doesn't seem like there's much we can do here until the upstream packages are all compatible too.

is airbnb config still the preferred config?
I always found it quite cumbersome. Had much more joy without airbnb and prettier and instead using antfu's config which includes eslint stylistic.

@woldtwerk if you want to propose changing our JS standards for something else please open an issue in https://www.drupal.org/project/issues/coding_standards → with some more details as to what the change is and why you think it is better.

Guess eslint is EOLing this weekend(tomorrow)?
https://eslint.org/blog/2024/09/eslint-v8-eol-version-support/

plugin-import rushed an update out this week.
No update on airbnb and comments asking for an update have just been marked as spam...