Implement MCP client

[rjambrecic]

Why are these changes needed?

Related issue number

Closes #1466

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.

[marklysze]

Amazing, thanks @rjambrecic!

[codecov]

Codecov Report

Attention: Patch coverage is 48.57143% with 36 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
autogen/mcp/mcp_client.py	38.88%	33 Missing ⚠️
autogen/tools/tool.py	50.00%	1 Missing and 1 partial ⚠️
autogen/interop/pydantic_ai/pydantic_ai.py	66.66%	1 Missing ⚠️

Files with missing lines	Coverage Δ
autogen/import_utils.py	89.54% <100.00%> (-0.46%)	⬇️
autogen/mcp/__init__.py	100.00% <100.00%> (ø)
autogen/interop/pydantic_ai/pydantic_ai.py	41.79% <66.66%> (ø)
autogen/tools/tool.py	86.66% <50.00%> (-2.81%)	⬇️
autogen/mcp/mcp_client.py	38.88% <38.88%> (ø)

... and 32 files with indirect coverage changes

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