Python: Update the AzureAIAgent packages, types, and APIs based on Az…

…ure SDK's new code (#12084)

### Motivation and Context

The Azure AI Agent Service is moving to GA soon. As part of that,
they've made several changes in the underlying APIs, which require the
use of new packages, updated type imports and some new underlying APIs.
This PR updates the AzureAIAgent to use the latest Azure SDK's new code.

- The client's connection string has been replaced with an endpoint.
- The `AzureAIAgentSettings`'s `model_deployment_name` was updated to
`deployment_name`.
- Tools are now imported from `from azure.ai.agents.models` instead of
`from azure.ai.projects.models`.
- Declarative spec handling for AzureAIAgent was updated based on the
new APIs.
- Unit tests were updated.

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### Description

Update the AzureAIAgent related code, samples and tests based on the
Azure SDK's latest APIs.
- Closes #12177 

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### Contribution Checklist

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- [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
- [ ] I didn't break anyone 😄

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Co-authored-by: Tao Chen <taochen@microsoft.com>