feat(utils): swap LegacyESLint out for FlatESLint as ESLint export#8972

JoshuaKGoldberg merged 3 commits intotypescript-eslint:v8typescript-eslint/typescript-eslint:v8from

JoshuaKGoldberg:utils-swap-flateslint-legacyeslintJoshuaKGoldberg/typescript-eslint:utils-swap-flateslint-legacyeslintCopy head branch name to clipboard