fix: support x-kubernetes-int-or-string type flag

[amyXia1994]

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

fix #20

• N
• Y

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

pkg/swagger/generator/types.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

The test case in pkg/kube_resource/generator/testdata/union_type is used to test the k8s int or str type flag

6. Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

support resolving x-kubernetes-int-or-string extension to KCL int | str type

[Peefy]

LGTM

[coveralls]

Pull Request Test Coverage Report for Build 2880765914

• 20 of 20 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 66.782%

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Totals
Change from base Build 2880741343:	0.2%
Covered Lines:	1938
Relevant Lines:	2902

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💛 - Coveralls

[chai2010]

LGTM

[Peefy]

LGTM