Add ChatCompletionCache along with AbstractStore for caching completi… #3578

Job	Run time
codecov (./packages/autogen-core)	1m 7s
check-proto-changes-python	2m 5s
docs (./packages/autogen-core)	1m 39s
codecov (./packages/autogen-magentic-one)	1m 52s
codecov (./packages/autogen-ext)	1h 0m 57s
codecov (./packages/autogen-agentchat)	1m 8s
docs-example-check (./packages/autogen-core)	2m 43s
format	54s
lint	51s
markdown-code-lint	2m 20s
mypy (./packages/autogen-core)	2m 43s
mypy (./packages/autogen-magentic-one)	1m 22s
pyright (./packages/autogen-core)	1m 0s
mypy (./packages/agbench)	1m 1s
samples-code-check	1m 6s
pyright (./packages/autogen-magentic-one)	59s
mypy (./packages/autogen-ext)	2m 14s
pyright (./packages/agbench)	59s
mypy (./packages/autogen-agentchat)	1m 30s
pyright (./packages/autogen-ext)	1m 1s
mypy (./packages/magentic-one-cli)	1m 31s
pyright (./packages/autogen-agentchat)	1m 28s
test (./packages/autogen-core)	58s
pyright (./packages/magentic-one-cli)	1m 7s
test (./packages/autogen-magentic-one)	1m 26s
test (./packages/autogen-ext)	3m 0s
test (./packages/autogen-agentchat)	1m 3s
	1h 40m 4s

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