[Agentserver] Make tracing dependencies optional

Currently there is an issue with the apistub check stemming from the
langchain-azure-ai dependency.

However, based on the code, `langchain_azure_ai` isn't needed for the
code to run, so it's fine to make this an optional dependency. It's
purely for enabling telemetry.

Author: pvaneck

sdk/agentserver/azure-ai-agentserver-langgraph/dev_requirements.txt

@@ -1,3 +1,4 @@
 -e ../../../eng/tools/azure-sdk-tools
 ../azure-ai-agentserver-core
-python-dotenv
+python-dotenv
+langchain-azure-ai[opentelemetry]>=0.1.4

sdk/agentserver/azure-ai-agentserver-langgraph/pyproject.toml

@@ -22,11 +22,15 @@ dependencies = [
     "azure-ai-agentserver-core",
     "langchain>0.3.5",
     "langchain-openai>0.3.10",
-    "langchain-azure-ai[opentelemetry]>=0.1.4",
     "langgraph>0.5.0",
     "opentelemetry-exporter-otlp-proto-http",
 ]
 
+[project.optional-dependencies]
+tracing = [
+    "langchain-azure-ai[opentelemetry]>=0.1.4",
+]
+
 [build-system]
 requires = ["setuptools>=69", "wheel"]
 build-backend = "setuptools.build_meta"
@@ -64,4 +68,4 @@ pyright = false
 verifytypes = false   # incompatible python version for -core
 verify_keywords = false
 mindependency = false  # depends on -core package
-whl_no_aio = false
+whl_no_aio = false