fix: rollback codegen script

[whynowy]

codegen stopped working after merging #2011, roll back the changes. @xdevxy

The new code-generator works quite differently from current approach, which needs some effort to make it work for us. It also differs a lot even between v0.29 and v0.30. We can stick with legacy approach for now, and fix it when the legacy approach is not supported any more.

v0.29: https://github.com/kubernetes/code-generator/blob/v0.29.5/examples/hack/update-codegen.sh#L44-L57 v0.30: https://github.com/kubernetes/code-generator/blob/v0.30.5/examples/hack/update-codegen.sh#L40-L53

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 64.30%. Comparing base (40e960a) to head (80eeac4). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2079 +/- ## ========================================== - Coverage 64.48% 64.30% -0.18% ========================================== Files 322 322 Lines 30145 30145 ========================================== - Hits 19438 19386 -52 - Misses 9684 9739 +55 + Partials 1023 1020 -3 ```

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