tests[patch]: run standard tests for embeddings and populate embeddings API ref (#28545)

plus minor updates to chat models and vector store API refs

libs/standard-tests/tests/unit_tests/test_embeddings.py

@@ -0,0 +1,26 @@
+from typing import Type
+
+from langchain_core.embeddings import DeterministicFakeEmbedding, Embeddings
+
+from langchain_tests.integration_tests import EmbeddingsIntegrationTests
+from langchain_tests.unit_tests import EmbeddingsUnitTests
+
+
+class TestFakeEmbeddingsUnit(EmbeddingsUnitTests):
+    @property
+    def embeddings_class(self) -> Type[Embeddings]:
+        return DeterministicFakeEmbedding
+
+    @property
+    def embedding_model_params(self) -> dict:
+        return {"size": 6}  # embedding dimension
+
+
+class TestFakeEmbeddingsIntegration(EmbeddingsIntegrationTests):
+    @property
+    def embeddings_class(self) -> Type[Embeddings]:
+        return DeterministicFakeEmbedding
+
+    @property
+    def embedding_model_params(self) -> dict:
+        return {"size": 6}