BUGFIX: Add import types and typevars from core (#13829) #10287

Job	Run time
Python 3.8 extended tests	5m 22s
Python 3.9 extended tests	2m 58s
Python 3.10 extended tests	10m 0s
Python 3.11 extended tests	10m 50s
test with unpublished langchain-core - Python 3.8	37s
test with unpublished langchain-core - Python 3.9	1m 9s
test with unpublished langchain-core - Python 3.10	45s
test with unpublished langchain-core - Python 3.11	1m 22s
compile-integration-tests / Python 3.8	35s
lint / build (3.8)	48s
compile-integration-tests / Python 3.9	43s
lint / build (3.11)	1m 34s
compile-integration-tests / Python 3.10	38s
pydantic-compatibility / Pydantic v1/v2 compatibility - Python 3.8	1m 2s
test / Python 3.8	48s
compile-integration-tests / Python 3.11	45s
pydantic-compatibility / Pydantic v1/v2 compatibility - Python 3.9	45s
test / Python 3.9	41s
pydantic-compatibility / Pydantic v1/v2 compatibility - Python 3.10	40s
test / Python 3.10	39s
test / Python 3.11	38s
pydantic-compatibility / Pydantic v1/v2 compatibility - Python 3.11	47s
	44m 6s

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