FunctionTool partial support

[nour-bouzid]

Why are these changes needed?

FunctionTool supports passing in a partial

Related issue number

Closes #5151

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#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.

[nour-bouzid]

@microsoft-github-policy-service agree company="Microsoft"

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.40%. Comparing base (2f1684b) to head (26b3dd7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5183   +/-   ##
=======================================
  Coverage   70.40%   70.40%           
=======================================
  Files         179      179           
  Lines       11615    11617    +2     
=======================================
+ Hits         8177     8179    +2     
  Misses       3438     3438           

Flag	Coverage Δ
unittests	70.40% <100.00%> (+<0.01%)	⬆️

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