Update the generator to swift 6.2

[Sencudra]

What's done?

As part of updating the track to support Swift 6.2, some work has been done on the generator:

1. All dependencies have been updated to their latest versions. A native dependency on swift-argument-parser
   has been added. The minimum macOS version required to run the generator is now macOS 13, as mandated by the swift-syntax library.
2. The code has been carefully rewritten in a safer, more modern, and more testable manner. The new implementation is covered by tests.
3. The ./bin/test_generator script has been updated to support the new argument list.
4. The Generator README.md has been updated to reflect these changes.

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[meatball133]

I will take a look at the changes later today, but I can if you want, can I ask Jeremy to add you to the organization so the prs doesn't automatically close.

[Sencudra]

I will take a look at the changes later today

I’d appreciate a review. I still need to sort out a newly surfaced issue. For the tests, I used Swift 6.2 feature of test names, but the CI doesn’t support Swift 6.2 yet. I’ll think about which option to choose — either temporarily revert to the old style of naming tests or update somehow to 6.2 without using prepared github actions.

but I can if you want, can I ask Jeremy to add you to the organization so the prs doesn't automatically close.

Yes, would be great, thank you.