fix: schema optional attribute validating recursively

[Peefy]

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

• N
• Y

• fix: schema optional attribute validating recursively

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

• kclvm/runtime/src/value/api.rs
• kclvm/runtime/src/value/mod.rs
• kclvm/runtime/src/value/val_schema.rs
• kclvm/runtime/src/value/walker.rs

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

• test/grammar/schema/optional_attr/fail_15/main.k
• test/grammar/schema/optional_attr/fail_16/main.k
• test/grammar/schema/optional_attr/fail_17/main.k
• test/grammar/schema/optional_attr/fail_18/main.k
• test/grammar/schema/optional_attr/fail_19/main.k
• test/grammar/schema/optional_attr/fail_20/main.k

[coveralls]

Pull Request Test Coverage Report for Build 7668313780

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.787%

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Totals
Change from base Build 7665256066:	0.0%
Covered Lines:	2293
Relevant Lines:	2612

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 7668313777

• -37 of 45 (17.78%) changed or added relevant lines in 3 files are covered.
• 241 unchanged lines in 8 files lost coverage.
• Overall coverage decreased (-15.5%) to 72.298%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
kclvm/runtime/src/value/val_schema.rs	3	4	75.0%
kclvm/runtime/src/value/api.rs	0	7	0.0%
kclvm/runtime/src/value/walker.rs	5	34	14.71%

Files with Coverage Reduction	New Missed Lines	%
compiler_base/error/src/diagnostic/diagnostic_message.rs	3	0.0%
compiler_base/error/src/diagnostic/components.rs	6	0.0%
compiler_base/error/src/errors.rs	8	0.0%
compiler_base/error/src/diagnostic/diagnostic_handler.rs	11	0.0%
compiler_base/session/src/lib.rs	26	58.06%
compiler_base/error/src/diagnostic/mod.rs	27	0.0%
compiler_base/error/src/diagnostic/style.rs	41	0.0%
compiler_base/error/src/emitter.rs	119	0.0%

Totals
Change from base Build 7665256066:	-15.5%
Covered Lines:	43747
Relevant Lines:	60509

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💛 - Coveralls