openai[minor]: implement langchain-openai package (#15503)

Todo

- [x] copy over integration tests
- [x] update docs with new instructions in #15513 
- [x] add linear ticket to bump core -> community, community->langchain,
and core->openai deps
- [ ] (optional): add `pip install langchain-openai` command to each
notebook using it
- [x] Update docstrings to not need `openai` install
- [x] Add serialization
- [x] deprecate old models

Contributor steps:

- [x] Add secret names to manual integrations workflow in
.github/workflows/_integration_test.yml
- [x] Add secrets to release workflow (for pre-release testing) in
.github/workflows/_release.yml

Maintainer steps (Contributors should not do these):

- [x] set up pypi and test pypi projects
- [x] add credential secrets to Github Actions
- [ ] add package to conda-forge


Functional changes to existing classes:

- now relies on openai client v1 (1.6.1) via concrete dep in
langchain-openai package

Codebase organization

- some function calling stuff moved to
`langchain_core.utils.function_calling` in order to be used in both
community and langchain-openai

libs/partners/openai/tests/unit_tests/embeddings/test_base.py

@@ -0,0 +1,18 @@
+import os
+
+import pytest
+
+from langchain_openai import OpenAIEmbeddings
+
+os.environ["OPENAI_API_KEY"] = "foo"
+
+
+def test_openai_invalid_model_kwargs() -> None:
+    with pytest.raises(ValueError):
+        OpenAIEmbeddings(model_kwargs={"model": "foo"})
+
+
+def test_openai_incorrect_field() -> None:
+    with pytest.warns(match="not default parameter"):
+        llm = OpenAIEmbeddings(foo="bar")
+    assert llm.model_kwargs == {"foo": "bar"}

libs/partners/openai/tests/unit_tests/embeddings/test_imports.py

@@ -0,0 +1,7 @@
+from langchain_openai.embeddings import __all__
+
+EXPECTED_ALL = ["OpenAIEmbeddings", "AzureOpenAIEmbeddings"]
+
+
+def test_all_imports() -> None:
+    assert sorted(EXPECTED_ALL) == sorted(__all__)