Upgrade ESLint config to v9 config system

[luc122c]

Describe the feature

From the ESLint docs:

We are transitioning to a new config system in ESLint v9.0.0. The config system shared on this page is currently the default but will be deprecated in v9.0.0.

There is no timetable for v9 release (see this blog post), however the new config system is "feature complete but not enabled by default" therefore, it seems desireable to think about switching to the new config system.

See:

• https://eslint.org/docs/latest/use/configure/configuration-files
• https://eslint.org/docs/latest/use/configure/configuration-files-new
• https://eslint.org/blog/2023/11/whats-coming-in-eslint-9.0.0
• When is ESLint 9 meant to be released? eslint/eslint#17468

Additional information

• Would you be willing to help implement this feature?
• Could this feature be implemented as a module?

Final checks

• Read the contribution guide.
• Check existing discussions and issues.

[manniL]

(This issue is used to track changes for the the ESLint config used for the nuxt framework itself, not https://github.com/nuxt/eslint-config)

[luc122c]

There is a tracker for plugin compatibility available: eslint/eslint#18093