Remove pydantic V1

[kumaranvpl]

Why are these changes needed?

Related issue number

Closes #457

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 90.90909% with 1 line in your changes missing coverage. Please review.

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

Flag	Coverage Δ
3.10	58.38% <90.90%> (+2.38%)	⬆️
3.11	29.18% <81.81%> (?)
3.12	27.43% <81.81%> (?)
3.13	41.53% <81.81%> (+7.83%)	⬆️
3.9	39.97% <81.81%> (+6.78%)	⬆️
anthropic	16.42% <54.54%> (?)
bedrock	16.79% <54.54%> (?)
cerebras	16.51% <54.54%> (?)
cohere	16.55% <54.54%> (?)
docs	28.78% <54.54%> (-0.07%)	⬇️
falkordb	15.85% <54.54%> (?)
gemini	16.50% <54.54%> (?)
graph-rag-falkor-db	28.22% <54.54%> (-0.07%)	⬇️
groq	16.52% <54.54%> (?)
interop	29.67% <54.54%> (-0.06%)	⬇️
jupyter-executor	30.94% <54.54%> (-0.06%)	⬇️
lmm	19.39% <54.54%> (?)
long-context	15.65% <54.54%> (?)
macos-latest	58.44% <90.90%> (+2.35%)	⬆️
mistral	16.23% <54.54%> (?)
neo4j	15.84% <54.54%> (?)
ollama	16.91% <54.54%> (?)
retrievechat	29.79% <54.54%> (-0.02%)	⬇️
retrievechat-mongodb	29.78% <54.54%> (+1.22%)	⬆️
retrievechat-pgvector	29.78% <54.54%> (+1.22%)	⬆️
retrievechat-qdrant	29.73% <54.54%> (+1.24%)	⬆️
teachable	15.83% <54.54%> (?)
together	16.56% <54.54%> (?)
twilio	28.43% <54.54%> (-0.07%)	⬇️
ubuntu-latest	58.46% <90.90%> (+2.39%)	⬆️
websurfer	18.78% <72.72%> (?)
windows-latest	56.07% <90.90%> (+2.40%)	⬆️

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

Files with missing lines	Coverage Δ
autogen/oai/client.py	55.39% <100.00%> (+1.92%)	⬆️
autogen/tools/function_utils.py	92.53% <100.00%> (+0.05%)	⬆️
autogen/agentchat/conversable_agent.py	69.67% <0.00%> (+0.91%)	⬆️

... and 8 files with indirect coverage changes