feat: support TypeScript config using tsx

[antfu]

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What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[x] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

• This PR implements RFC: feat: Add support for TypeScript config files rfcs#117 but uses tsx instead of jiti
• Alternative to feat: Add support for TS config files #18134

Support loading eslint.config.ts eslint.config.mts eslint.config.cts files powered by tsx. The support is opt-in by users, where they need to install tsx explicitly (we include it as optional peer deps instead of dependencies)

Based on my previous experiments with eslint-ts-patch(which supports swapping different loaders like jiti tsx bundle-require, feel free to try them out). So for I see that tsx is the best approach as it uses Node's native loader API, support full ESM, top-level await, and does not generate temporary files.

The only downside is that it uses Node's API, which has only been available since v20.8.0 and v18.19.0. But considering this is an opt-in feature, it should be fine, and the ecosystem should catch up soon.

Is there anything you'd like reviewers to focus on?

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[nzakas]

Marking as a draft to avoid accidental merging, as there is an RFC being discussed.