fix(sync): bump go-kong + fill auto fields with nil

[samugi]

Summary

bump go-kong to 0.59.0

use go-kong utils to fill auto fields with nil in the config sent to the CP. The rest of the default values are still not filled in the configuration that is sent out, as they are meant to be filled by the CP itself.

Full changelog

• [Implement ...]
• [Fix ...]

Issues resolved

https://konghq.atlassian.net/browse/KAG-5317

Documentation

• [ ] Link to the website documentation PR

Testing

• [ ] Unit tests
• [ ] E2E tests
• [ ] Manual testing on Universal
• [ ] Manual testing on Kubernetes

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 29.96%. Comparing base (0b1b75f) to head (80d5c9c). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/diff/diff.go	0.00%	8 Missing :warning:
pkg/types/plugin.go	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #139 +/- ## ========================================== - Coverage 29.97% 29.96% -0.01% ========================================== Files 106 106 Lines 12581 12583 +2 ========================================== Hits 3771 3771 - Misses 8350 8352 +2 Partials 460 460 ```

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