Support function_call in `autogen/agent` (#1091)

* update funccall

* code format

* update to comments

* update notebook

* remove test for py3.7

* allow funccall to class functions

* add test and clean up notebook

* revise notebook and test

* update

* update mathagent

* Update flaml/autogen/agent/agent.py

Co-authored-by: Chi Wang <wang.chi@microsoft.com>

* Update flaml/autogen/agent/user_proxy_agent.py

Co-authored-by: Chi Wang <wang.chi@microsoft.com>

* revise to comments

* revise function call design, notebook and test. add doc

* code format

* ad message_to_dict function

* update mathproxyagent

* revise docstr

* update

* Update flaml/autogen/agent/math_user_proxy_agent.py

Co-authored-by: Chi Wang <wang.chi@microsoft.com>

* Update flaml/autogen/agent/math_user_proxy_agent.py

Co-authored-by: Qingyun Wu <qingyun.wu@psu.edu>

* Update flaml/autogen/agent/user_proxy_agent.py

Co-authored-by: Qingyun Wu <qingyun.wu@psu.edu>

* simply funccall in userproxyagent, rewind auto-gen.md, revise to comments

* code format

* update

* remove notebook for another pr

* revise oai_conversation part  in agent, revise function exec in user_proxy_agent

* update test_funccall

* update

* update

* fix pydantic version

* Update test/autogen/test_agent.py

Co-authored-by: Chi Wang <wang.chi@microsoft.com>

* fix bug

* fix bug

* update

* update is_termination_msg to accept dict

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Co-authored-by: Chi Wang <wang.chi@microsoft.com>
Co-authored-by: Qingyun Wu <qingyun.wu@psu.edu>
Co-authored-by: Li Jiang <bnujli@gmail.com>