Add module level docstrings #2317

Job	Run time
pyright (./packages/autogen-core)	55s
pyright (./packages/autogen-magentic-one)	1m 8s
pyright (./packages/agbench)	52s
check-proto-changes-python	1m 5s
pyright (./packages/autogen-ext)	59s
pyright (./packages/autogen-agentchat)	53s
docs (./packages/autogen-core)	1m 23s
format	46s
docs-example-check (./packages/autogen-core)	2m 23s
lint	50s
mypy (./packages/autogen-core)	2m 7s
test (./packages/autogen-core)	1m 3s
mypy (./packages/autogen-magentic-one)	1m 9s
test (./packages/autogen-magentic-one)	1m 22s
mypy (./packages/agbench)	1m 0s
test (./packages/autogen-ext)	2m 6s
mypy (./packages/autogen-ext)	1m 49s
test (./packages/autogen-agentchat)	1m 8s
mypy (./packages/autogen-agentchat)	1m 2s
	24m 0s

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