feature: Support LangGraph Azure OpenAI in aws-genai plugin

[marct83]

🔖 Feature description

Add support for Azure OpenAI in the Gen AI Plugin.

🎤 Context

It would be beneficial for some to be able to use Azure Chat OpenAI in the Gen AI plugin as that is what our org uses.

Langchain supports azure openai: https://python.langchain.com/docs/integrations/chat/azure_chat_openai/

✌️ Possible Implementation

Create a new interface with the config:
https://github.com/awslabs/backstage-plugins-for-aws/blob/main/plugins/genai/agent-langgraph/src/config/types.ts

Add a new config function:
https://github.com/awslabs/backstage-plugins-for-aws/blob/main/plugins/genai/agent-langgraph/src/config/config.ts

Create new AzureOpenAiModel function:
https://github.com/awslabs/backstage-plugins-for-aws/blob/main/plugins/genai/agent-langgraph/src/LangGraphReactAgentType.ts#L184

Add new else if for the new model:
https://github.com/awslabs/backstage-plugins-for-aws/blob/main/plugins/genai/agent-langgraph/src/LangGraphReactAgentType.ts#L88

[niallthomson]

@marct83 I'd be open to a PR for this but won't have the bandwidth to implement ourselves.

[marct83]

@marct83 I'd be open to a PR for this but won't have the bandwidth to implement ourselves.

Let me see what I can do.