Community: Updating Azure Retriever and Docs to be Azure AI Search instead of Azure Cognitive Search (#19925)

Last year Microsoft [changed the
name](https://learn.microsoft.com/en-us/azure/search/search-what-is-azure-search)
of Azure Cognitive Search to Azure AI Search. This PR updates the
Langchain Azure Retriever API and it's associated docs to reflect this
change. It may be confusing for users to see the name Cognitive here and
AI in the Microsoft documentation which is why this is needed. I've also
added a more detailed example to the Azure retriever doc page.

There are more places that need a similar update but I'm breaking it up
so the PRs are not too big 😄 Fixing my errors from the previous PR.

Twitter: @marlene_zw

Two new tests added to test backward compatibility in
`libs/community/tests/integration_tests/retrievers/test_azure_cognitive_search.py`

---------

Co-authored-by: Chester Curme <chester.curme@gmail.com>

libs/langchain/langchain/retrievers/__init__.py

@@ -60,6 +60,7 @@ __all__ = [
     "AmazonKnowledgeBasesRetriever",
     "ArceeRetriever",
     "ArxivRetriever",
+    "AzureAISearchRetriever",
     "AzureCognitiveSearchRetriever",
     "ChatGPTPluginRetriever",
     "ContextualCompressionRetriever",

libs/langchain/langchain/retrievers/azure_ai_search.py

@@ -0,0 +1,6 @@
+from langchain_community.retrievers.azure_ai_search import (
+    AzureAISearchRetriever,
+    AzureCognitiveSearchRetriever,
+)
+
+__all__ = ["AzureAISearchRetriever", "AzureCognitiveSearchRetriever"]

libs/langchain/langchain/retrievers/azure_cognitive_search.py

@@ -1,5 +0,0 @@
-from langchain_community.retrievers.azure_cognitive_search import (
-    AzureCognitiveSearchRetriever,
-)
-
-__all__ = ["AzureCognitiveSearchRetriever"]

libs/langchain/tests/unit_tests/retrievers/test_imports.py

@@ -6,6 +6,7 @@ EXPECTED_ALL = [
     "AmazonKnowledgeBasesRetriever",
     "ArceeRetriever",
     "ArxivRetriever",
+    "AzureAISearchRetriever",
     "AzureCognitiveSearchRetriever",
     "ChatGPTPluginRetriever",
     "ContextualCompressionRetriever",