feat!: support ESLint 9 flat config

[haoqunjiang]

Due to the heavy maintenance burden, I'd like to drop support for plain <script> blocks in .vue by default.
Also, the default configuration should be the recommended one, instead of eslint-recommended (which isn't a recommended config by the upstream typescript-eslint anyway).

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My rollout plan for ESLint 9 support in create-vue:

• @vue/eslint-config-prettier new version feat!: add support for ESLint Flat Config; drop `.eslintrc* support eslint-config-prettier#22
• @vue/eslint-config-typescript new version with basic functionality, as laid out in this PR. (I'm afraid I can't get the *-type-checked configurations right on the first try; I'm not sure about the performance in large projects either).
• @vue/create-eslint-config experimental flat config support
• create-vue new version before ESLint 8 EOL. feat: support ESLint 9 Flat Config create-vue#573
• Finish @vue/eslint-config-typescript features and performance improvements.
• Work on @vue/eslint-config-standard and @vue/eslint-config-airbnb. I can't guarantee a timeframe for these 2 projects, though. I will likely work on the standard config first because the upstream library has already shipped flag config support.

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Closes #72
Closes #73
Closes #75
Closes #76
Closes #80