feat: lsp hover for schema attr default value

[He1pa]

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

• N
• Y Show default values from models preview in the KCL language server #1578
  

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

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

[coveralls]

Pull Request Test Coverage Report for Build 11011660451

Details

• 42 of 45 (93.33%) changed or added relevant lines in 9 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.03%) to 70.629%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
kclvm/sema/src/resolver/global.rs	3	6	50.0%

Files with Coverage Reduction	New Missed Lines	%
kclvm/tools/src/LSP/src/tests.rs	1	98.61%

Totals
Change from base Build 11009839852:	0.03%
Covered Lines:	51374
Relevant Lines:	72738

---

💛 - Coveralls