community: Update OCI data science integration (#27083)

This PR updates the integration with OCI data science model deployment
service.

- Update LLM to support streaming and async calls.
- Added chat model.
- Updated tests and docs.
- Updated `libs/community/scripts/check_pydantic.sh` since the use of
`@pre_init` is removed from existing integration.
- Updated `libs/community/extended_testing_deps.txt` as this integration
requires `langchain_openai`.

---------

Co-authored-by: MING KANG <ming.kang@oracle.com>
Co-authored-by: Dmitrii Cherkasov <dmitrii.cherkasov@oracle.com>
Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/scripts/check_pydantic.sh

@@ -20,7 +20,7 @@ count=$(git grep -E '(@root_validator)|(@validator)|(@field_validator)|(@pre_ini
 # PRs that increase the current count will not be accepted.
 # PRs that decrease update the code in the repository
 # and allow decreasing the count of are welcome!
-current_count=128
+current_count=127
 
 if [ "$count" -gt "$current_count" ]; then
   echo "The PR seems to be introducing new usage of @root_validator and/or @field_validator."