doc gen: migrate from kcl-go.getSchemaTypeMapping API to kpm.GetKclPackage API

[amyXia1994]

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

• N
• Y
  related to [Feature] KCL doc tool: extract, generate document of KCL packages #139

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

change the command line description:

• cmds/kcl-go/command/cmd_doc.go

migrate to kpm API:

• go.mod
• go.sum
• pkg/tools/gen/gendoc.go
• pkg/tools/gen/genopenapi.go

add more test cases:

• pkg/tools/gen/gendoc_test.go
• pkg/tools/gen/testdata/doc/k8s/...
• pkg/tools/gen/testdata/doc/pkg/...
• pkg/tools/gen/testdata/doc/reimport/...

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

doc gen:

• migrate from kcl-go.getSchemaTypeMapping API to kpm.GetKclPackage API
• add more test cases

• 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

[coveralls]

Pull Request Test Coverage Report for Build 5949055246

• 43 of 46 (93.48%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 63.778%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/tools/gen/gendoc.go	15	18	83.33%

Totals
Change from base Build 5939213107:	0.03%
Covered Lines:	2421
Relevant Lines:	3796

---

💛 - Coveralls

[Peefy]

LGTM