Update to ESlint v9 and new config format (flatconfig)

[nicholasio]

Is your enhancement related to a problem? Please describe.

https://eslint.org/blog/2024/04/eslint-v9.0.0-released/

Designs

No response

Describe alternatives you've considered

No response

Code of Conduct

• [X] I agree to follow this project's Code of Conduct