[Enhancement]Fix OAI V2 client tool call extract logic from message_retrieval

[randombet]

Why are these changes needed?

Related issue number

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/latest/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

❌ Patch coverage is 6.77966% with 55 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
autogen/llm_clients/openai_completions_client.py	6.77%	55 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (482cbe7) and HEAD (a362f93). Click for more details.

HEAD has 510 uploads less than BASE

Flag	BASE (482cbe7)	HEAD (a362f93)
core-without-llm	6	0
ubuntu-latest	56	3
3.11	48	0
3.10	46	3
macos-latest	55	0
docs	6	0
optional-deps	6	0
windows-latest	55	0
3.13	39	0
agent-eval	1	0
teachable	3	0
gpt-assistant-agent	3	0
llama-index-agent	3	0
together	12	0
retrievechat	6	0
retrievechat-qdrant	6	0
3.12	33	0
mistral	12	0
retrievechat-couchbase	2	0
retrievechat-mongodb	2	0
retrievechat-pgvector	2	0
anthropic	12	0
long-context	3	0
websurfer	12	0
lmm	3	0
gemini	12	0
cerebras	12	0
cohere	12	0
swarm	12	0
bedrock	12	0
groq	12	0
ollama	12	0

Files with missing lines	Coverage Δ
autogen/llm_clients/openai_completions_client.py	13.63% <6.77%> (-69.02%)	⬇️

... and 155 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.