Feat: Add JSON output test for vet command

[atsai1220]

Hello!

I'm looking for some guidance on contributing towards #249. I've created a test case here but ultimately it seems like error messages are structured and generated in kcl-lang/kcl/kclvm/error/src/error.rs#L67.

Hope to get the ball rolling with authors' guidance. I imagine updating the error format in the rust repository will have a lot of impact on any downstream services that receive those messages. The first attempt was to try and parse and reformat to JSON the output from kcl-lang/cli/cmd/kcl/commands/vet.go#L111. Thoughts?

I've added a test case here with a suggested output format for JSON in test/e2e/test_suites/test_kcl_vet_output_json_1/stderr. Welcome any feedback.

Thank you!

1. Does this PR affect any open issues?(Y/N) and add issue references:

• N
• Y
  fix Vet command should support structured output formats #249

2. What is the scope of this PR (e.g. component or file name):

cmd/kcl/commands/vet.go

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Other

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• N
• Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• Unit test
• Integration test
• Benchmark (add benchmark stats below)
• Manual test (add detailed scripts or steps below)
• Other

[Peefy]

The CI failed. Could u pls fix it?