fix: incorrect async type checking and pydantic version conflict in function.py

[kausmeows]

(#3790)

Instead we now gracefully handle this conflict and log it for reference.

• Fixed comment to accurately reflect code logic: now mentions both async generators and coroutines
• Fixed incorrect usage of isasyncgen() vs isasyncgenfunction() when checking function objects
• Fixed incorrect usage of isgenerator() vs isgeneratorfunction() when checking function objects
• Added missing imports for iscoroutinefunction and isgeneratorfunction
• Removed unused isasyncgen import in _build_nested_execution_chain_async

These fixes ensure proper type checking for async/generator functions and improve cache handling logic.[修复] 修正函数异步类型检查错误并更新注释，并改进了缓存处理逻辑。

Summary

These fixes ensure proper type checking for async/generator functions and improve cache handling logic.

Type of change

• [ *] Bug fix
• New feature
• Breaking change
• Improvement
• Model update
• Other:

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Checklist

• [*] Code complies with style guidelines
• [*] Ran format/validation scripts (./scripts/format.sh and ./scripts/validate.sh)
• [*] Self-review completed
• [*] Documentation updated (comments, docstrings)
• [*] Examples and guides: Relevant cookbook examples have been included or updated (if applicable)
• [*] Tested in clean environment
• [*] Tests added/updated (if applicable)

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Additional Notes

none

Summary

Describe key changes, mention related issues or motivation for the changes.

(If applicable, issue number: #____)

Type of change

• Bug fix
• New feature
• Breaking change
• Improvement
• Model update
• Other:

---

Checklist

• Code complies with style guidelines
• Ran format/validation scripts (./scripts/format.sh and ./scripts/validate.sh)
• Self-review completed
• Documentation updated (comments, docstrings)
• Examples and guides: Relevant cookbook examples have been included or updated (if applicable)
• Tested in clean environment
• Tests added/updated (if applicable)

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Additional Notes

Add any important context (deployment instructions, screenshots, security considerations, etc.)