Switch to ESLint flat config

https://eslint.org/docs/latest/use/configure/configuration-files-new

Blockers:

• https://github.com/prettier/eslint-plugin-prettier/commit/3856413420d3d026e5ae84f29c4bd0d558697135
• https://github.com/typescript-eslint/typescript-eslint/commit/8ef5f4bffcf0904a28ada92a224a378d309407a4
• https://github.com/typescript-eslint/typescript-eslint/commit/18c3216485c381dd0215cfa7099f33bc721c8efe