feat: add api 'GetFullSchemaType' to support external package in kcl doc

[zong-zhe]

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

• N
• Y

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

pkg/kcl/api.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]

cc @zong-zhe, I have upgrade the kcl artifact to v0.7.0-beta.2 and check passed. Ref:

• chore: bump kcl artifact lib to v0.7.0-beta.2 #191
• feat: add validate APIs #189

After this PR has been merged, we can trigger a kcl-go v0.7.0-beta.2 tag for kpm. Then we can trigger a 0.5.0 kpm tag for kcl-go. After all, the v0.7.0 kcl-go tag release!

[coveralls]

Pull Request Test Coverage Report for Build 7043204534

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
To ensure accuracy in future PRs, please see these guidelines.
A quick fix for this PR: rebase it; your next report should be accurate.

• 12 of 16 (75.0%) changed or added relevant lines in 1 file are covered.
• 9 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.6%) to 63.617%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/kcl/api.go	12	16	75.0%

Files with Coverage Reduction	New Missed Lines	%
kclvm.go	3	70.83%
pkg/tools/validate/validate.go	6	86.36%

Totals
Change from base Build 7001857205:	0.6%
Covered Lines:	2740
Relevant Lines:	4307

---

💛 - Coveralls

[Peefy]

LGTM