Beta/mcp support

[stepacool]

Why are these changes needed?

MCP Servers lifecycle mapping to tools, invited by @Lancetnik

Related issue number

Beta

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 66.34615% with 70 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
autogen/beta/tools/toolkits/mcp_server/toolkit.py	56.73%	38 Missing and 7 partials ⚠️
...togen/beta/tools/toolkits/mcp_server/connection.py	62.68%	19 Missing and 6 partials ⚠️

Files with missing lines	Coverage Δ
autogen/beta/config/gemini/mappers.py	83.05% <ø> (ø)
autogen/beta/tools/__init__.py	100.00% <100.00%> (ø)
autogen/beta/tools/toolkits/__init__.py	100.00% <100.00%> (ø)
autogen/beta/tools/toolkits/mcp_server/__init__.py	100.00% <100.00%> (ø)
autogen/beta/tools/toolkits/mcp_server/types.py	100.00% <100.00%> (ø)
...togen/beta/tools/toolkits/mcp_server/connection.py	62.68% <62.68%> (ø)
autogen/beta/tools/toolkits/mcp_server/toolkit.py	56.73% <56.73%> (ø)

... and 54 files with indirect coverage changes

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