Supporting callable message (#1852)

* add message field

* send

* message func doc str

* test dict message

* retiring soon

* generate_init_message docstr

* remove todo

* update notebook

* CompressibleAgent

* update notebook

* add test

* retrieve agent

* update test

* summary_method args

* summary

* carryover

* dict message

* update nested doc

* generate_init_message

* fix typo

* update docs for mathchat

* Fix missing message

* Add docstrings

* model

* notebook

* default naming

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Co-authored-by: Chi Wang <wang.chi@microsoft.com>
Co-authored-by: kevin666aa <yrwu000627@gmail.com>
Co-authored-by: Li Jiang <bnujli@gmail.com>
Co-authored-by: Li Jiang <lijiang1@microsoft.com>