Add guide for workbench and mcp & bug fixes for create_mcp_server_session

[ekzhu]

Add user guide for workbench and mcp

*Also fixed a bug in create_mcp_server_session that included "type" in the parameters Resolves: #6392

[codecov]

Codecov Report

Attention: Patch coverage is 54.54545% with 5 lines in your changes missing coverage. Please review.

Project coverage is 78.36%. Comparing base (f059262) to head (efd4d85).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
.../autogen-core/src/autogen_core/tools/_workbench.py	60.00%	4 Missing ⚠️
.../autogen-ext/src/autogen_ext/tools/mcp/_session.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6392      +/-   ##
==========================================
- Coverage   78.37%   78.36%   -0.02%     
==========================================
  Files         221      221              
  Lines       16010    16020      +10     
==========================================
+ Hits        12548    12554       +6     
- Misses       3462     3466       +4     

Flag	Coverage Δ
unittests	78.36% <54.54%> (-0.02%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 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.