Python: Add missing fields to AzureAIAgentSettings (#12211)

### Motivation and Context

Some fields were missing from `AzureAIAgentSettings`, which caused
errors during placeholder replacement in the declarative agent.

https://github.com/microsoft/semantic-kernel/blob/6efcc847c56d742a12dec871bd715319a599533c/python/semantic_kernel/agents/azure_ai/azure_ai_agent.py#L568-L575

### Description

- Add the missing fields to `AzureAIAgentSettings`.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

Author: KanchiShimono

python/semantic_kernel/agents/azure_ai/azure_ai_agent_settings.py

@@ -20,4 +20,8 @@ class AzureAIAgentSettings(KernelBaseSettings):
 
     model_deployment_name: str
     endpoint: str | None = None
+    agent_id: str | None = None
+    bing_connection_id: str | None = None
+    azure_ai_search_connection_id: str | None = None
+    azure_ai_search_index_name: str | None = None
     api_version: str | None = None