feat: add builtin io function workdir()

[zong-zhe]

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

• N
• Y

re #1049

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

add built-in function workdir().

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]

LGTM

[coveralls]

Pull Request Test Coverage Report for Build 7984591037

Details

• 43 of 66 (65.15%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 71.808%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
kclvm/runtime/src/_kclvm_addr.rs	0	2	0.0%
kclvm/runtime/src/context/mod.rs	0	3	0.0%
kclvm/runtime/src/context/api.rs	0	9	0.0%
kclvm/runtime/src/file/mod.rs	0	9	0.0%

Totals
Change from base Build 7983193669:	-0.01%
Covered Lines:	44245
Relevant Lines:	61616

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💛 - Coveralls