[Bug fix]: Fix tool registration from a Tool

[marklysze]

Why are these changes needed?

There's a bug with tools and swarm function registration: Tool does not support __name__ but it has _name, so updated ConversableAgent._add_single_function to cater for this.

Related issue number

N/A

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/docs/contributor-guide/documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
autogen/agentchat/conversable_agent.py	0.00%	0 Missing and 1 partial ⚠️

Flag	Coverage Δ
3.10	58.59% <0.00%> (+2.70%)	⬆️
3.11	30.79% <0.00%> (?)
3.12	27.61% <0.00%> (?)
3.13	42.51% <0.00%> (+7.86%)	⬆️
3.9	55.38% <0.00%> (+21.65%)	⬆️
anthropic	37.32% <0.00%> (?)
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bedrock	16.73% <0.00%> (?)
browser_use	29.40% <0.00%> (-0.01%)	⬇️
cerebras	16.45% <0.00%> (?)
cohere	16.49% <0.00%> (?)
crawl4ai	29.61% <0.00%> (-0.01%)	⬇️
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graph-rag-falkor-db	28.03% <0.00%> (-0.01%)	⬇️
groq	16.47% <0.00%> (?)
interop	29.47% <0.00%> (-0.01%)	⬇️
jupyter-executor	30.72% <0.00%> (-0.01%)	⬇️
lmm	19.80% <0.00%> (?)
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retrievechat	29.58% <0.00%> (+0.04%)	⬆️
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retrievechat-pgvector	29.57% <0.00%> (+1.26%)	⬆️
retrievechat-qdrant	29.52% <0.00%> (+1.28%)	⬆️
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together	16.50% <0.00%> (?)
twilio	28.24% <0.00%> (-0.01%)	⬇️
ubuntu-latest	66.61% <0.00%> (+10.31%)	⬆️
websurfer	18.71% <0.00%> (?)
windows-latest	56.63% <0.00%> (+2.70%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
autogen/agentchat/conversable_agent.py	77.53% <0.00%> (+12.71%)	⬆️

... and 28 files with indirect coverage changes